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Is the glucose produced from photosynthesis considered an aqueous solution when written as a chemical reaction?

Is the glucose produced from photosynthesis considered an aqueous solution when written as a chemical reaction?


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In the very simplified reaction for photosynthesis, the states of the reactants and products are clear to me except for glucose. Inside a plant, it would be dissolved in water, so would it be an aqueous solution or be considered a precipitate in some way? In the reaction

$$ce{6CO_2 {_{(g)}} + 6H_2O{_{(l)}} ightarrow C_6H_{12}O_6{_{(?)}} + 6O_2{_{(g)}}}$$

what would I put in the place of the question mark?


Lakhmir Singh Solutions For Class 10 Chemistry Chapter 1 Chemical Reactions And Equations

This chapter deals with various chemical reactions, their examples and corresponding chemical equations. A chemical reaction is a process in which new substances with new properties are formed. It involves rearrangement of atoms and breaking of chemical bonds.

In a chemical reaction mainly there will be two sides, one is reactant side and the other one is the product side. Two reactants combine to form products or reactants are transformed into products in a chemical reaction. The method of representing a chemical reaction with the help of symbols and formulae of the substance involved is known as chemical equations.


The function H(t) = −16t^2 + 90t + 50 shows the height H(t), in feet, of a projectile after t seconds. A second object moves in the air along a path represented by g(t) = 28 + 48.8t, where g(t) is the height, in feet, of the object from the ground at

You have been given a sample of unknown molarity. Calculate the molarity of a solution which has been prepared by dissolving 8.75 moles of sodium chloride in enough water to produce a solution of 6.22l. 2. You have a sample which consists of 428g sodium


Decomposition Reactions

A decomposition reaction is a reaction in which a compound breaks down into two or more simpler substances. The general form of a decomposition reaction is:

Most decomposition reactions require an input of energy in the form of heat, light, or electricity.

Binary compounds are compounds composed of just two elements. The simplest kind of decomposition reaction is when a binary compound decomposes into its elements. Mercury (II) oxide, a red solid, decomposes when heated to produce mercury and oxygen gas.

[2 ce left( s ight) ightarrow 2 ce left( l ight) + ce left( g ight)]

A reaction is also considered to be a decomposition reaction even when one or more of the products is still a compound. A metal carbonate decomposes into a metal oxide and carbon dioxide gas. For example, calcium carbonate decomposes into calcium oxide and carbon dioxide.

[ce left( s ight) ightarrow ce left( s ight) + ce left( g ight)]

Metal hydroxides decompose on heating to yield metal oxides and water. Sodium hydroxide decomposes to produce sodium oxide and water.

[2 ce left( s ight) ightarrow ce left( s ight) + ce left( g ight)]


Why Some People Consider Dissolving Salt a Physical Change

If you search online for the answer to this question, you'll see about an equal number of responses arguing that dissolving salt is a physical change as opposed to a chemical change. The confusion arises because of one common test to help distinguish chemical changes from physical ones: whether or not the starting material in the change may be recovered using only physical processes. If you boil the water off of a salt solution, you'll obtain salt.


Biology for AP Courses

Which of the following components is not used by both plants and cyanobacteria to carry out photosynthesis?

a. carbon dioxide
b. chlorophyll
c. chloroplasts
d. water

Problem 2

Why are chemoautotrophs not considered the same as photoautotrophs if they both extract energy and make sugars?

a. Chemoautotrophs use wavelengths of light not available to photoautotrophs.
b. Chemoautotrophs extract energy from inorganic chemical compounds.
c. Photoautotrophs prefer the blue side of the
d. Photoautotrophs make glucose, while chemoautophs make galactose.

Problem 3

3. In which compartment of the plant cell do the light-independent reactions of photosynthesis take place?
a. mesophyll
b. outer membrane
c. stroma
d. thylakoid

Problem 4

a. the Calvin cycle
b. the inner membrane
c. stroma
d. thylakoids

Problem 5

What are two major products of photosynthesis?

a. chlorophyll and oxygen
b. oxygen and carbon dioxide
c. stroma
d. thylakoids

Problem 6

What is the primary energy source for cells?

a. glucose
b. starch
c. sucrose
d. triglycerides

Problem 7

Which portion of the electromagnetic radiation originating from the sun is harmful to living tissues?

a. blue
b. green
c. infrared
d. ultraviolet

Problem 8

The amount of energy in a wave can be measured using what trait?

a. color intensity
b. distance from trough to crest
c. the amount of sugar produced
d. wavelength

Problem 9

What portion of the electromagnetic radiation emitted by the sun has the least energy?
a. gamma
b. infrared
c. radio
d. X-rays

Problem 10

What is the function of carotenoids in photosynthesis?

a. They supplement chlorophyll absorption.
b. They are visible in the fall during leaf color changes.
c. They absorb excess energy and dissipate it as heat.
d. They limit chlorophyll absorption.

Problem 11

Which of the following structures is not a component of a photosystem?
a. antenna molecule
b. ATP synthase
c. primary electron acceptor
d. reaction center

Problem 12

Which complex is not involved in producing the electromotive force of ATP synthesis?
a. ATP synthase
b. cytochrome complex
c. Photosystem I
d. Photosystem II

Problem 13

What can be calculated from a wavelength measurement of light?

a. a specific portion of the visible spectrum
b. color intensity
c. the amount of energy of a wave of light
d. the distance from trough to crest of the wave

Problem 14

Which molecule must enter the Calvin cycle continually for the light-independent reactions to take
place?

a. CO2
b. RuBisCO
c. RuBP
d. 3-PGA

Problem 15

Which order of molecular conversions is correct for the Calvin cycle?
a. $operatorname+mathrm 3 mathrm

ightarrow 3 mathrm ightarrow$ sugar
b. $mathrm ightarrow mathrm_ <2> ightarrow mathrm ightarrow mathrm 3 mathrm

$
c. $operatorname+mathrm_ <2> ightarrow[mathrm] 3-mathrm ightarrow mathrm 3 mathrm

$
$mathrm_ <2> ightarrow 3-mathrm ightarrow mathrm ightarrow mathrm 3 mathrm

$

Problem 16

Which statement correctly describes carbon fixation?
a. the conversion of $mathrm_<2>$ into an organic compound
b. the use of RuBisCO to form 3 -PGA
c. the production of carbohydrate molecules from G3P
d. the use of ATP and NADPH to reduce $mathrm_<2>$

Problem 17

Which substance catalyzes carbon fixation?

Problem 18

Which pathway is used by both plants and animals?

a. carbon fixation
b. cellular respiration
c. photosystem II
d. photosynthesis

Problem 19

Which of the following organisms is a heterotroph?

a. Cyanobacterium
b. intestinal bacteria
c. kelp
d. pond algae

Problem 20

What is the role of ribulose-1, 5 -bisphosphate, abreviated RuBisCO, in photosynthesis?
a. It catalyzes the reaction between $mathrm_<2>$ and ribulose bisphosphate (RuBP).
b. It catalyzes the reaction that produces glyceraldehyde 3 -phosphate (G3P).
c. It catalyzes the reaction that regenerates RuBP.
d. It catalyzes the reaction utilizing ATP and NADPH.

Problem 21

What is the product of the Calvin cycle?

a. Glucose
b. Glyceraldehyde-3-Phosphate
c. Phosphoglycerate (PGA)
d. sucrose

Problem 22

What are the roles of ATP and NADPH in photosynthesis?

a. ATP and NADPH are forms of chemical energy
produced from the light dependent reactions to
be used in the light independent reactions that
produce sugars.
b. ATP and NADPH are forms of chemical energy
produced from the light independent reactions,
to be used in the light dependent reactions that
produce sugars.
c. ATP and NADPH are forms of chemical energy
produced from the light dependent reactions to
be used in the light independent reactions that
produce proteins.
d. ATP and NADPH are forms of chemical energy
produced from the light dependent reactions to
be used in the light independent reactions that
use sugars as reactants.

Problem 23

What is the overall outcome of the light reactions in photosynthesis?

a. NADPH and ATP molecules are produced during the light reactions and are used to power
the light independent reactions.
b. NADPH and ATP molecules are produced during the light reactions, which are used to
power the light dependent reactions.
c. Sugar and ATP are produced during the light reactions, which are used to power the light
independent reactions.
d. Carbon dioxide and NADPH are produced during the light reactions, which are used to
power the light dependent reactions.

Problem 24

How does the equation relate to both photosynthesis and cellular respiration?

a. Photosynthesis utilizes energy to build carbohydrates while cellular respiration
metabolizes carbohydrates.
b. Photosynthesis utilizes energy to metabolize carbohydrates while cellular respiration builds
carbohydrates.
c. Photosynthesis and cellular respiration both utilize carbon dioxide and water to produce
carbohydrates.
d. Photosynthesis and cellular respiration both metabolize carbohydrates to produce carbon
dioxide and water

Problem 25

How is the energy from the sun transported within chloroplasts?

a. When photons strike photosystem (PS) II, pigments pass the light energy to chlorophyll a
molecules that excite an electron, which is then passed to the electron transport chain. The
cytochrome complex transfers protons across the thylakoid membrane and transfers electrons
from PS-II to PS-I. The products of the light dependent reaction are used to power the Calvin
cycle to produce glucose.
b. When photons strike photosystem (PS) I, pigments pass the light energy to chlorophyll,
molecules that excite electrons, which is then passed to the electron transport chain. The
cytochrome complex then transfers protons across the thylakoid membrane and transfers
electrons from PS-II to PS-I. The products of the light dependent reaction are used to power the
Calvin cycle to produce glucose.
c. When photons strike photosystem (PS) II, pigments pass the light energy to chlorophyll
molecules that in turn excite electrons, which are then passed to the electron transport chain. The
cytochrome complex transfers protons across the thylakoid membrane and transfers electrons
from PS-I to PS-II. The products of the light dependent reaction are used to power the Calvin
cycle to produce glucose.
d. When photons strike photosystem (PS) II, pigments pass the light energy to chlorophyll
molecules that excite electrons, which is then passed to the electron transport chain. The
cytochrome complex transfers protons across the thylakoid membrane and transfers electrons
from PS II to PS I. The products of the light independent reaction are used to power the
Calvin cycle to produce glucose.

Problem 26

Explain why X-rays and ultraviolet light wavelengths are dangerous to living tissues.

a. UV and X-rays are high energy waves that penetrate the tissues and damage cells.
b. UV and X-rays are low energy waves that penetrate the tissues and damage cells.
c. UV and X-rays cannot penetrate tissues and thus damage the cells.
d. UV and X-rays can penetrate tissues and thus do not damage the cells.

Problem 27

If a plant were to be exposed to only red light, would photosynthesis be possible?

a. Photosynthesis does not take place.
b. The rate of photosynthesis increases sharply.
c. The rate of photosynthesis decreases drastically.
d. The rate of photosynthesis decreases and then increases.

Problem 28

Describe the electron transfer pathway from photosystem II to photosystem I in the light-dependent
reactions.

a. After splitting water in PS-II, high energy electrons are delivered through the chloroplast
electron transport chain to PS-I.
b. After splitting water in PS-I, high energy electrons are delivered through the chloroplast
electron transport chain to PS-II.
c. After the photosynthesis reaction, the released products like glucose help in the transfer of
electrons from PS-II to PS-I.
d. After the completion of the light dependent reactions, the electrons are transferred from PSII to PS-I.

Problem 29

What will happen to a plant leaf that loses $mathrm_<2>$ too quickly?

a. no effect on the rate of photosynthesis
b. Photosynthesis will slow down or stop possibly.
c. Photosynthesis will increase exponentially.
d. Photosynthesis will decrease and then increase.

Problem 30

Carbon, in the form of $mathrm_<2>,$ must be taken from the atmosphere and attached to an existing organic molecule in the Calvin cycle. Therefore, the carbon is bound to the molecule. The products of the cycle only occur because of the added carbon. What are the products of the Calvin cycle and what is regenerated?

a. The product of the Calvin cycle is glyceraldehyde-3 phosphate and RuBP is regenerated.
b. The product of the Calvin cycle is glyceraldehyde-3 phosphate and RuBisCO is regenerated.
c. The product of the Calvin cycle is a 3-PGA molecule and glyceraldehyde-3 phosphate is regenerated.
d. The product of the Calvin cycle is glyceraldehyde-3 phosphate and oxygen is regenerated.

Problem 31

How do desert plants prevent water loss from the heat, which would compromise photosynthesis?

a. by using CAM photosynthesis and by closing stomatal pores during the night
b. by using CAM photosynthesis and by opening of stomatal pores during the night
c. by using CAM photosynthesis and by keeping stomatal pores closed at all times
d. by bypassing CAM photosynthesis and by keeping stomatal pores closed at night

Problem 32

Why are carnivores, such as lions, dependent on photosynthesis to survive?

a. because the prey of lions are generally herbivores which depend on heterotrophs
b. because the prey of lions are generally smaller carnivorous animals which depend on nonphotosynthetic organisms
c. because the prey of lions are generally herbivores which depend on autotrophs
d. because the prey of lions are generally omnivores that depend only on autotrophs.

Problem 33

Why does it take three turns of the Calvin cycle to produce G3P, the initial product of photosynthesis?

a. To fix enough carbon to export one G3P molecule.
b. To fix enough oxygen to export one G3P molecule.
c. To produce RuBisCO as an end product.
d. To produce ATP and NADPH for fixation of G3P.

Problem 34

Photosynthesis and cellular respiration are found throughout the eukaryotic world. They are complementary to each other because they each use products of the other process. What do the two pathways share?

a. chloroplasts and mitochondria
b. Photosystems I and II
c. the cytochrome complex
d. thylakoids

Problem 35

What evidence exists that the evolution of photosynthesis and cellular respiration support the concept that there is a common ancestry for all organisms?

a. All organisms perform cellular respiration, using oxygen and glucose, which are produced by
photosynthesis.
b. All organisms perform cellular respiration using carbon dioxide and glucose, which are produced
by photosynthesis.
c. All organisms perform cellular respiration using oxygen and lipids, which are produced by
photosynthesis.
d. All organisms perform cellular respiration using carbon dioxide and lipids, which are produced
by photosynthesis.

Problem 36

Correctly label the indicated parts of a chloroplast.

a. A.stroma, B. outer membrane, C. granum, D. thylakoid, E. inner membrane
b. A. outer membrane, B. stroma, C. granum, D. thylakoid, E. inner membrane
c. A. outer membrane, B. stroma, C. granum, D. inner membrane, E. thylakoid
d. A. stroma, B. outer membrane, C. inner membrane, D. granum, E. thylakoid

Problem 37

What cellular features and processes are similar in both photosynthesis and cellular respiration?

a. Both processes are contained in organelles with single membranes, and both use a version of the
cytochrome complex.
b. Both processes are contained in organelles with double membranes, and neither use a version of
the cytochrome complex.
c. Both processes are contained in organelles with double membranes, and use a version of the
cytochrome complex.
d. Both processes are contained in organelles with single membranes, and neither use a version of
the cytochrome complex.

Problem 38

Why do the light-dependent reactions of photosynthesis take place in the thylakoid?

a. Photosystem I is anchored to the membrane, but not photosystem II.
b. The cytochrome complex requires a membrane for chemiosmosis to occur.
c. The light-dependent reactions depend on the presence of carbon dioxide.
d. Light energy is absorbed by the thylakoid membrane.

Problem 39

Metabolic pathways both produce and use energy to perform their reactions. How does the Calvin cycle help to harness, store, and use energy in its pathway?

a. The Calvin cycle harnesses energy in the form of 6 ATP and 6 NADPH that are used to produce
Fructose- 3 - phosphate (F3P) molecules. These store the energy captured from photosynthesis.
The cycle uses this energy to regenerate RuBP.
b. The Calvin cycle harnesses energy in the form of 6 ATP and 6 NADPH that are used to produce
Glyceraldehyde-3- phosphate (GA3P) molecules. These store the energy captured from
photosynthesis. The cycle uses this energy to regenerate RuBP.
c. The Calvin cycle harnesses energy in the form of 3 ATP and 3 NADPH that are used to produce
Glyceraldehyde-3- phosphate (GA3P) molecules. These store the energy captured from
photosynthesis. The cycle uses this energy to regenerate the RuBP.
d. The Calvin cycle harnesses energy in the form of 6 ATP and 3 NADPH that are used to produce
Glyceraldehyde-3- phosphate (GA3P) molecules. These store energy captured from photosynthesis. The cycle uses this energy to regenerate RuBP.

Problem 40

Based on Figure 8.18, which would most likely cause a plant to run out of NADP?

a. missing the ATP synthase enzyme
b. exposure to light
c. A lack of water would prevent $mathrm^<+>$ and $mathrm^<+>$ from forming NADPH
d. not enough $mathrm_<2>$

Problem 41

As temperatures increase, gases such as $mathrm_<2>$ diffuse faster. As a result, plant leaves will lose $mathrm_<2>$ at a faster rate than normal, If the amount of light impacting on the leaf and the amount of water available is adequate, predict how this loss of gas will affect photosynthesis in the leaf.
a. Loss of gases, mainly $mathrm_<2>,$ will not affect photosynthesis in the leaf, as adequate amounts of water and light are still present which will let the Calvin cycle run smoothly.
b. Loss of gases, mainly $mathrm_<2>,$ will affect photosynthesis in the leaf, as the Calvin cycle will become faster to compensate for the loss.
C. Loss of gases, mainly $mathrm_<2>,$ will not affect photosynthesis in the leaf, as stored reservoirs of $mathrm_<2>$ in the leaf can be utilized in such times.
d. Loss of gases, mainly $mathrm_<2>,$ will affect photosynthesis in the leaf, as the Calvin cycle will slow down and possibly stop because of inadequate carbon to fix in the system.

Problem 42

How do the cytochrome complex components involved in photosynthesis contribute to the electron transport chain?
a. Photosystem I excites the electron as it moves down the electron transport chain into
Photosystem II.
b. Plastoquinone and plastocyanine perform redox reactions that allow the electron to move down the electron transport chain into Photosystem I.
d. RuBisCO excites the electron as it moves down the electron transport chain into Photosystem II.

Problem 43

Discuss how membranes in chloroplasts contribute to the organelles' essential functions.
a. The inner membrane contains the chemicals needed for the Calvin cycle and also components of the light dependent reactions. The thylakoid membrane contains photosystems I and II, as well as the enzyme $mathrm^<+>$ reductase.
b. The inner membrane contains only the chemicals needed for the Calvin cycle. The thylakoid
membrane contains components of the light dependent reactions, photosystems I and II, and
the enzyme $mathrm^<+>$ reductase.
C. The inner membrane contains components of the light dependent reactions as well as
photosystems I and II. The thylakoid membrane contains the chemicals needed for the Calvin
cycle and also the enzyme NAD $^<+>$ reductase.
d. The inner membrane contains the chemicals needed for the Calvin cycle, components of the light dependent reactions and photosystems I and II. The thylakoid membrane contains the
enzyme $mathrm^<+>$ reductase.

Problem 44

If the absorption spectrum of photosynthetic pigments was restricted to the green portion of the spectrum, which pigment or pigments would be affected the least?
a. carotenoids
b. chlorophyll a
c. chlorophyll b
d. chlorophyll c

Problem 45

Describe the passage of energy from light until it is captured in the primary electron acceptor.
a. Chlorophyll molecules in the photosystems are excited and pass the energy to the primary
electron acceptor where the energy is used to excite electrons from the splitting of water.
b. Chlorophyll a molecules in the photosystems are excited and pass the energy to the primary
electron acceptor where the energy is used to excite electrons from the splitting of water.
C. Chlorophyll b molecules in the photosystems are excited and pass the energy to the primary
electron acceptor where the energy is used to excite electrons from the splitting of water.
d. Chlorophyll molecules in the photosystems absorb light and get excited in the primary
electron acceptor from where the energy is used to excite electrons from the splitting of water.

Problem 46

On a hot, dry day, plants close their stomata to conserve water. Explain the connection between the oxidation of water in photosystem II of the light-dependent reactions and the synthesis of glyceraldehyde-3-phosphate (G3PA) in the light-independent reactions. Predict the
effect of closed stomata on the synthesis of G3PA and justify the prediction.

Problem 47

The emergence of photosynthetic organisms is recorded in layers of sedimentary rock known as a banded iron formation. Dark-colored and iron-rich bands composed of hematite (Fe2O3) and magnetite (Fe3O4) only a few millimeters thick alternate with light-colored and
iron-poor shale or chert. Hematite and magnetite can form precipitates from water that has a high concentration of dissolved oxygen. Shale and chert can form under conditions that have high concentrations of carbonates (CO3 -2). These banded iron formations appeared 3.7
billion years ago (and became less common 1.8 billion years ago). Justify the claim that these sedimentary rock formations reveal early Earth conditions.

Problem 48

The following diagram summarizes the light reactions of photosynthesis.
The diagram shows light-dependent reactions of photosynthesis, including the reaction centers, electron transport chains, and the overall reactions within each of these. The free energy per electron is shown for the oxidation-reduction reactions. The free change of the captured radiant energy is shown.
2NADP+ + 2H
+ + 2H2 O + 3ADP + 3Pi ?
O2 + 4H
+ + 2NADPH + 3ATP
A. In the overall mass balance equation for the light reactions shown above, identify the source of electrons for the synthesis of NADPH.
B. Calculate the number of electrons transferred in this reaction.
C. Using the free energies per electron displayed, calculate the free energy change of the lightdependent reactions.
D. Given that the free energy change for the hydrolysis of ATP is -31.5 kJ/mole and the free
energy change for the formation of NADPH from NADP+ is 18 kJ/mole, calculate the total
production of free energy for the light reactions.
E. Using this definition of energy efficiency, calculate the efficiency of the light reaction of
photosynthesis: energy efficiency = free energy produced/energy input

Problem 49

Algae can be used for food and fuel. To maximize profit from algae production under artificial light, researchers proposed an experiment to determine the dependence of the efficiency of the process used to grow the algae on light intensity (“brightness”) that will be
purchased from the electric company. The algae will be grown on a flat sheet that will be continuously washed with dissolved carbon dioxide and nutrients. Light-emitting diodes (LEDs) will be used to illuminate the growth sheet. Photodiodes placed above and below the sheet will be used to detect light transmitted through and reflected from the algal mat. The intensity of light can be varied, and the algae can be removed, filtered, and dried. The amount of stored energy in the algal mats can be determined by calorimetry.
A. Identify a useful definition of efficiency for this study and justify your choice.
B. Frequencies of light emitted by the LEDs will not be variables but must be specified for the construction of the apparatus. Identify the frequencies of light that should be used in the experiment and justify your choice.
C. Evaluate the claim that the experiment is based on the assumption that there is an upper limit on the intensity of light used to support growth of algae. Predict a possible effect on algal growth if light with too great an intensity is used and justify the prediction.
D. Design an experiment by describing a procedure that can be used to determine the relationship between light intensity and efficiency

Problem 50

The classical theory of evolution is based on a gradual transformation, the accumulation of many random mutations that are selected. The biological evidence for evolution is overwhelming, particularly when one considers what has not changed: core conserved
characteristics.
A. Describe three conserved characteristics common to both chloroplasts and mitochondria Some hypotheses that have been proposed to account for biological diversity are saltatory, involving sudden changes, rather than gradualist. In defense of the classical gradualist theory of evolution, nearly all biologists in the late 1960s rejected the theory of endosymbiosis as presented by Lynn Margulis in 1967.
B. Suppose that you want to disprove the theory of
endosymbiosis.
Explain how the following evidence could disprove the
theory:
i. a “transitional species” with cellular features that are intermediate cells with and without mitochondria
ii. a “transitional organelle” with some features, such as compartmentalized metabolic processes, but not other features, such as DNA
Explain how the following evidence supports the theory
of endosymbiosis:
iii. bacteria live within your intestines, but you still have a separate identity
iv. no one has directly observed the fusion of two organisms in which a single organism results.

Problem 51

Discovering the carbon-fixation reactions (or lightindependent reactions) of photosynthesis earned Melvin Calvin a Nobel Prize in 1961. The isolation and
identification of the products of algae exposed to 14C revealed the path of carbon in photosynthesis. 14C was fed to the algal culture in the form of bicarbonate ion (HCO3 - ).
To agitate the culture, air, which contains CO2, was bubbled through the system, so there were two sources of carbon.
Since Calvin’s experiment, research has focused on the way carbon from a solution containing bicarbonate ions is absorbed by algae. In aqueous solution, the bicarbonate anion (HCO3 - ) is in equilibrium with dissolved CO2 as shown in the equation below:
$H^<+>+H C O_<3>^ <->Longleftrightarrow H_ <2>O+C O_<2>$
In a later experiment, Larsson and Axelsson (1999) used acetazolamide (AZ), a carbonate anhydrase inhibitor, to inhibit enzymes that convert bicarbonate into carbon dioxide. They also used disulfonate (DIDS), an inhibitor of the transport of anions, such as the bicarbonate ion, through the plasma membrane.
A. Pose a scientific question that can be pursued with AZ and DIDS in terms of the path of carbon in photosynthesis.
B. The plasma membrane is permeable to the nonpolar, uncharged carbon dioxide molecule. However, the concentration of carbon dioxide in solution can be very small. Explain how the enzyme carbonate anhydrase can increase the availability of carbon dioxide to the cell.
C. Larsson and Axelsson conducted experiments in which the growth medium was fixed at two different pH levels and determined the effects of AZ and DIDS on the rate of photosynthesis by measuring oxygen concentrations at various times. The results are shown in the two graphs
below. The arrows indicate the time points during which $mathrm_<3>$ - , AZ, and DIDS were added to each system.
Figure 8.23 This figure displays the effects of AZ and DIDS on the rate of photosynthesis of two systems, system A and system B, in a line graph. The line graph plots the oxygen
concentration over time. In which system, A or B, is there a strong reliance on the bicarbonate ion as the mechanism of carbon uptake by the cell? Justify your answer using the data.
D. If both systems are dosed with the same concentrations of bicarbonate ion, in which system, A or B, is the pH higher? Justify your answer using the data and the bicarbonate-carbon dioxide equilibrium equation.


What Exactly is O​​​​smosis ?

Osmosis is the movement of water, and some other liquids, across a semipermeable membrane such as a cell wall. Osmosis doesn’t require extra energy or pressure to occur. It’s one type of passive transport that allows some cells to move nutrients in or wastes out without using the body’s precious energy reserves. Osmosis moves down the concentration gradient.

Osmosis usually happens when water outside, or inside, a cell is more concentrated and helps move nutrients and wastes in and out of the cell. This is a crucial way cells are fed or grow. Osmosis isn't just about feeding cells and helping them develop. It can occur between two compartments when the water level in one cell is higher, or a concentration of elements is suspended in water outside a cell.

In mammals, osmosis effects the number of nutrients, typically, inside or outside a cell. Through osmosis, cells maintain a steady flow of nutrients into the cavity for repairs or growth. It's only the primary way cells get rid of wastes. In plants, osmosis is usually the only way water is absorbed from the ground and sent up the plant to feed cells. Osmosis does not work without water.


It's common to indicate the state of matter in a chemical equation by including parentheses and an abbreviation right after a chemical formula. This can be seen in the following equation:

Hydrogen and oxygen are indicated by (g), which means they are gases. Water is marked (l), which means it is a liquid. Another symbol you may see is (aq), which means the chemical species is in water — or an aqueous solution. The (aq) symbol is a sort of shorthand notation for aqueous solutions so that water doesn't have to ​be included in the equation. It's particularly common when ions are present in a solution.


Lactic acid, HC3H5O3(aq) is a weak acid that gives yougurt its sour taste(Yeeeeecccckkk). Calculate the pH of a 0.0010 mol/L solution of Lactic acid. The Ka for lactic acid is 1.4 x 10^-4 For Further Reading chemistry - DrBob222, Saturday, April 5, 2008 at

The main result of aerobic respiration is the 1 conversion of radiant energy into chemical energy 2 production of lactic acid as an end product 3 storage of energy in a polysaccharide 4 production of ATP from the breakdown of glucose


Extra Questions for Class 10 Science Chapter 1 Chemical Reactions and Equations with Answers Solutions

Chemical Reactions and Equations Extra Questions Very Short Answer Type

Question 1.
Why is the combustion of Liquified Petroleum Gas (LPG) a chemical change?
Answer:
Combustion of Liquified Petroleum Gas (LPG) is a chemical change because, after its combustion, a new substance is formed and cannot be turned back into LPG.

Question 2.
What is wrong with the following equation?
Mg + O ➝ MgO
Identify the mistake and balance the equation.
Answer:
In this equation, oxygen should be in molecular form (O2).
2Mg + O2 ➝ 2MgO.

Question 3.
What is meant by the skeletal equation?
Answer:
The equation where the number of atoms of each element on both sides of a chemical equation is not equal is called a skeletal equation.

Question 4.
Potassium chlorate (KClO3) on heating forms potassium chloride and oxygen. Write a balanced equation for these reactions
Answer:
2KClO3(s) → 2KCI(s) + 3O2(g)

Question 5.
What do you observe when magnesium ribbon is burnt?
Answer:
When magnesium ribbon is burnt, formation of white powder is observed along with white dazzling flame.

Question 6.
On heating blue coloured powder of copper (II) nitrate in a boiling tube, copper oxide (black), oxygen gas and a brown gas ‘X’ is formed. Identify the brown gas ‘X’.
Answer:

‘X’ is nitrogen dioxide gas.

Question 7.
Convey the following information in the form of a balanced chemical equation:
“An aqueous solution of ferrous sulphate reacts with an aqueous solution of sodium hydroxide to form a precipitate of ferrous hydroxide and sodium sulphate remains in solution.”
Answer:
FeSO4(aq) + 2NaOH (aq) → Fe(OH)2(s) + Na2SO4(aq)

Question 8.
Balance the following chemical equation :

Answer:

Question 9.
Give one example of a combination reaction which is also exothermic.
Answer:
When quicklime or calcium oxide (Cao) reacts with water, slaked lime (Ca(OH)2] is formed. During this reaction a large amount of heat is released. So, this reaction is an exothermic reaction.

Question 10.
Why will the colour of heated copper powder become black when air is passed over it?
Answer:
When copper powder is heated in the presence of air, black copper oxide is formed.

Question 11.
What is the difference between the following two types of reactions ?
AgNO3 + HCl → AgCl + HNO3
Mg + 2HCl → MgCl2 + H2
Answer:
The first reaction is a double displacement reaction whereas second reaction is a single displacement reaction.

Question 12.
Why is hydrogen peroxide kept in coloured bottles ?
Answer:
This is done in order to cut off light because hydrogen peroxide decomposes into water and oxygen in the presence of light.

Question 13.
Consider the following reactions :
(i) Fe + CuSO4 → FeSO4 + Cu
(ii) Cu + FeSO4 → CuSO4 + Fe
Which of these two reactions will take place and why?
Answer:
Reaction (i) will take place. This is because Fe (iron) is more reactive than Cu (copper) and so it can displace Cu from its compound (CuSO4). On the other hand, copper (Cu) cannot displace iron (Fe), so reaction,
(ii) will not take place.

Question 14.
Give one example of a reaction which is a double displacement reaction as well as a precipitation reaction.
Answer:

Question 15.
Why is photosynthesis considered an endothermic reaction ?
Answer:
Photosynthesis is an endothermic reaction because energy, in the form of sunlight is absorbed during the process of photosynthesis by green plants.

Question 16.
What type of reaction is represented by the digestion of food in our body?
Answer:
Decomposition reaction.

Question 17.
How will you test for the gas which is liberated when hydrochloric acid reacts with an active metal ?
Answer:
When an active metal like Zn reacts with HCl, the gas produced burns with a pop sound which indicates that it is hydrogen gas.
Zn(s) + 2HCl (aq) → ZnCl2(s) + H2 (g)

Question 18.
Can a double displacement reaction take place when the products are highly soluble or highly ionised?
Answer:
No, double displacement reaction takes place when there is a formation of a slightly soluble salt.

Question 19.
What changes in the colour of iron nails and copper sulphate solution do you observe after keeping the iron nails dipped in copper sulphate solution for about 3O minutes ?
Answer:
Iron nails become brownish in colour and the blue colour of copper sulphate solution fades. This is because iron displaces copper from copper sulphate solution and forms ferrous sulphate which is light green in colour.

Question 20.
Name the oxidising and reducing agent in the following reaction :
2H2S + SO2 ➝ 2H2O + 3S ↓.
Answer:
H2S is the reducing agent while SO, is the oxidising agent.

Question 21.
Explain with reason as to why the blue colour of aqueous copper sulphate solution fades away slowly when an iron rod is dipped into it.
Answer:
Iron being more reactive than copper displaces copper from copper sulphate solution. Thus, blue colour of the solution fades and copper metal gets deposited.

Question 22.
Explain redox reaction with example.
Answer:
Redox Reaction: Those reactions in which oxidation and reduction take place simul taneously, are called redox reactons. Exp.

Chemical Reactions and Equations Extra Questions Short Answer Type

Question 1.
Which among the following are physical or chemical changes ?
(a) Evaporation of petrol
(b) Burning of Liquefied Petroleum Gas (LPG)
(c) Heating of an iron rod to red hot
(d) Curdling of milk
(e) Sublimation of solid ammonium chloride
Answer:
(a) Physical change
(b) Chemical change
(c) Physical change
(d) Chemical change
(e) Physical change.

Question 2.
How do we come to know that a chemical reaction has taken place ?
Answer:
The presence of any of the following changes helps us to determine that a chemical reaction has taken place.
(i) Formation of new substance(s)
(ii) Change in state
(iii) Change in colour
(iv) Change in temperature
(v) Formation of a precipitate
(vi) Evolution of a gas For example, if on mixing two substances a gas is evolved, then we can say that a chemical reaction has taken place.

Question 3.
Which among the following changes are exothermic or endothermic in nature ?
(a) Decomposition of ferrous sulphate :
(b) Dilution of sulphuric acid
(c) Dissolution of sodium hydroxide in water
(d) Dissolution of ammonium chloride in water
Answer:
(a) is endothermic as heat is absorbed in these changes.
(b) is exothermic as heat is released in these changes.
(c) is exothermic as heat is released in these changes.
(d) is endothermic as heat is absorbed in these changes.

Question 4.
What is an oxidation reaction ? Give an example of oxidation reaction. Is oxidation an exothermic or an endothermic reaction ?
Answer:
The reaction in which oxygen combines with other elements or compounds is known as an oxidation reaction. For example, burning of hydrogen is an oxidation process in which hydrogen combines with oxygen to form water.
2H2(g) + O2 (g) ➝ 2H2O(l)
Oxidation reactions are exothermic.

Question 5.
Why do fire flies glow at night?
Answer:
Fire flies have a protein which in the presence of enzyme undergoes aerial oxidation. This is a chemical reaction which involves emission of visible light. Therefore, fire flies glow at night.

Question 6.
Give reasons :
(a) Aluminium is a reactive metal but is still used for packing food articles.
(b) Red litmus paper turns blue when touched with aqueous solution of magnesium oxide.
Answer:
(a) On exposure to air, aluminium forms a hard protective layer of aluminium oxide (AI2O3) which prevent further oxidation.
(b) Magnesium oxide is an oxide of a metal, so, it is basic in nature. Due to its basic character it turns red litmus paper blue when touched with its aqueous solution.

Question 7.
Why do we store silver chloride in dark coloured bottles ?
Answer:
Silver chloride on exposure to sunlight may decompose as per the following reaction.
2AgCl(s) ➝ 2Ag(s) + Cl2(g)
Therefore, it is stored in dark coloured bottles.

Question 8.
Giving an example, list two informations which make a chemical reaction more useful ?
Answer:
(i) Indicating physical state of reactants and products.
(ii) Indicating energy change in terms of heat.

Question 9.
Complete the missing components/variables given as x and y in the following reactions :
(i) Pb(NO2)2(aq) + 2KI (aq) → PbI2(x) + 2KNO2(y)
(ii) Cu(s) + 2AgNO3 (aq) +Cu(NO3)2(aq) + x (s)
(iii) Zn(s) + H2SO4 (aq) + ZnSO4(x) + H2 (y)
(iv) CaCO3(s) → CaO (s) + CO2(g)
Answer:
(i) x – (s) y – (aq)
(ii) x – 2Ag
(iii) x – (aq) y – (g)
(iv) x – Heat

Question 10.
Zinc liberates hydrogen gas when reacted with dilute hydrochloric acid, whereas copper does not. Explain why.
Answer:
Zinc is above hydrogen whereas copper is below hydrogen in the activity series of metals. That is why zinc displaces hydrogen from dilute hydrochloric acid, while copper does not.
Zn + HCl → ZnCl2 + H2
Cu + HCl → No reaction

Question 11.
On adding dilute HCl to copper oxide powder, the soluton formed is blue green. Predict the new compound formed which imparts a blue-green colour to the solution.
Answer:
The new compound formed is copper (II) chloride (CuCl2), which imparts blue-green colour to the solution.

Question 12.
A solution of potassium chloride when mixed with silver nitrate solution, an insoluble white substance is formed. Write the chemical reaction involved and also mention the type of the chemical reaction.
Answer:
KCl(aq) + AgNO3(aq) → AgCl(s) + KNO3(aq)
It is a double displacement and precipitation reaction.

Question 13.
Ferrous sulphate decomposes with the evolution of a gas having a. characteristic odour of burning sulphur. Write the chemical reaction involved and identify the type of reaction.
Answer:

It is a thermal decomposition reaction.

Question 14.
Identify the substance oxidised, substance reduced, oxidising agent and reducing agent:
MnO2 + 4HCl → MnCl2 + 2H2O + Cl2
Answer:
Substance oxidised : HCl
Substance reduced : MnO2
Oxidising agent : MnO2
Reducing agent : HCl

Question 15.
Grapes hanging on the plant do not ferment but after being plucked from the plant can be fermented. Under what conditions do these grapes ferment? Is it a chemical or a physical change ?
Answer:
Grapes when attached to the plants are living and therefore, their own immune system prevents fermentation. The microbes can grow in the plucked grapes and under anaerobic conditions these can be fermented. This is a chemical change.

Question 16.
A copper coin was kept dipped in silver nitrate solution for a few hours/ days. What will happen to the copper coin ? What will happen to the colour of the solution ?
Answer:
Copper is more reactive than silver. Hence, it displaces silver from the silver nitrate solution according to the given reaction.

The silver thus formed is deposited on the surface of copper, thereby giving it a white shining appearance.
The solution becomes blue due to the formation of copper nitrate..

Question 17.
Identify the reducing agent in the following reactions.
(a) 4NH3 + 5O2 → 4NO + 6H2O
(b) H2O + F2 → HF + HOF
(c) Fe2O3 + 3CO → 2Fe + 3CO2
(d) 2H2 + O2 → 2H2O
Answer:
(a) Ammonia (NH3)
(b) Water (H2O) as F2 is getting reduced to HF
(c) Carbon monoxide (CO)
(d) Hydrogen (H2)

Question 18.
What is the role of a catalyst in a chemical reaction ?
Answer:
Catalyst changes (usually increases but sometimes decreases) the rate of a chemical reaction without itself being consumed in the reaction.

Question 19.
Translate the following statements into chemical equations and balance them:
(i) Lead nitrate reacts with sulphuric acid to form a precipitate of lead sulphate and nitric acid. :
(ii) Magnesium burns in the presence of nitrogen to form magnesium nitride.
(iii) Aluminium metal strip is added in hydrochloric acid to produce aluminium chloride and hydrogen gas.
Answer:
(i) Pb(NO3)2(aq) + H2SO4 (aq) ➝ PbSO4(s) + 2HNO3 (aq)
(ii) 3Mg(s) + N2 (g) ∆ ➝ Mg3 N2(s)
(iii) 2Al(s) + 6HCl (aq) + 2AlCl3(aq) ➝ 3H2(g)

Question 20.
Write the balanced chemical equations for the following reactions :
(a) Sodium carbonate on reaction with hydrochloric acid in equal molar concentrations gives sodium chloride and sodium hydrogen carbonate.
(b) Sodium hydrogencarbonate on reaction with hydrochloric acid gives sodium chloride, water and liberates carbon dioxide.
(c) Copper sulphate on treatment with potassium iodide precipitates cuprous iodide (Cu2I)2 liberates iodine gas and also forms potassium sulphate.
Answer:
(a) Na2CO3 + HCl → NaCl + NaHCO3
(b) NaHCO3 + HCl + NaCl + H2O + CO2
(c) 2CusO4 + 4KI → Cu2l2 + 2K2SO4 + l2

Question 21.
Write the balanced chemical equations for the following reactions and identify the type of reaction in each case.
(i) Nitrogen gas is treated with hydrogen gas in the presence of a catalyst at 773 K to form ammonia gas.
(ii) Sodium hydroxide solution is treated with acetic acid to form sodium acetate and water.
(iii) Ethanol is warmed with ethanoic acid to form ethyl acetate in the presence of concentrated H2SO4.
(iv) Ethene is burnt in the presence of oxygen to form carbon dioxide, water and releases heat and light.
Answer:

Redox reaction/Combustion reaction

Question 22.
Write the balanced chemical equations for the following reactions and identify the type of reaction in each case.
(a) Thermit reaction, iron (III) oxide reacts with aluminium and gives molten iron and aluminium oxide.
(b) Magnesium ribbon is burnt in an atmosphere of nitrogen gas to form solid magnesium nitride.
(c) Chlorine gas is passed in an aqueous potassium iodide solution to form potassium chloride solution and solid iodine.
(d) Ethanol is burnt in air to form carbon dioxide, water and releases heat.
Answer:
(a) Fe2O3(s) + 2Al(s) + AI2O3(s) + 2Fe(l) + Heat Displacement reaction
(b) 3Mg(s) + N2 (g) → Mg3 N2(s) Combination reaction
(c) 2KI(aq) + CI2(g) → 2Kc1(aq) + I2(s) Displacement reaction
(d) C2H5OH(I) + 3O2(g) → 2CO2(g) + 3H2O(I) + Heat Combustion reaction

Question 23.
Name the type of chemical reaction represented by the following equation:
(i) CaO + H2O → Ca(OH)2
(ii) 3BaCl, + AI2(SO2) → 2AICI3 + 3BaSO4

Answer:
(i) Combination reaction.
(ii) Double displacement reaction.
(iii) Thermal decomposition reaction.

Question 24.
Translate the following statements into chemical equations and then balance the equations :
(i) Phosphorus burns in oxygen to give phosphorus pentoxide.
(ii) Aluminium metal replaces iron from ferric oxide, Fe2O3, giving aluminium oxide and iron.
(iii) Carbon disulphide burns in air to give carbon dioxide and sulphur dioxide.
(iv) Barium chloride reacts with zinc sulphate to give zinc chloride and barium sulphate.
Answer:
(i) P4 + 5O2 → 2P2O5
(ii) 2Al + Fe2O3 → AI2O3 + 2Fe
(iii) CS2 + 3O2 → CO2 + 2SO2
(iv) BaČl2 + ZnSO2 → ZnCl2 + BaSO4

Question 25.
(i) What is observed when a solution of potassium iodide is added to a solution of lead nitrate taken in a test tube ?
(ii) What type of reaction is this?
(iii) Write a balanced chemical equation to represent the above reaction.
Answer:
(i) A yellow precipitate of lead iodide (PbI,) is formed.
(ii) Precipitation reaction/Double displacement reaction.

Question 26.
(i) What happens when silver nitrate solution is added to sodium chloride solution ? Write the equation for the reaction which takes place.
(ii) Name the type of reaction involved.
Answer:
(i) When silver nitrate solution is added to sodium chloride solution, a white precipitate of silver chloride is formed along with sodium nitrate solution.

(ii) This is double displacement reaction and precipitation reaction.

Question 27.
(i) What is the colour of ferrous sulphate crystals ? How does this colour change after heating ?
(ii) Name the products formed on strongly heating ferrous sulphate crystals. What type of chemical reaction occurs in this change?
Answer:
(i) The colour of ferrous sulphate crystals is green. On heating, FeSO47H2O first decomposes to form anhydrous ferrous sulphate (FeSO) which is white in colour.
(ii) The products formed on strongly heating ferrous sulphate crystals are ferric oxide, sulphur dioxide and sulphur trioxide.

This is a type of thermal decomposition reaction.

Question 29.
Solid calcium oxide was taken in a container and water was added slowly to it
(i) State the two observations made in the experiment.
(ii) Write the name and chemical formula of the product formed.
Answer:
(i) Following are the two observations :
(a) Calcium oxide (Cao) reacts vigorously with water to form slaked lime.
(b) The container becomes hot because a large amount of heat is released during this reaction.
(ii) The product formed is slaked lime for which the chemical formula is Ca(OH)2.

Question 30.
A substance X, which is an oxide of a group 2 element, is used intensively in the cement industry. This element is present in bones also. On treatment with water it forms a solution which turns red litmus blue. Identify X and also write the chemical reactions involved.
Answer:
X is calcium oxide, also called quick lime. It reacts with water to form calcium hydroxide which is basic in nature. So, it turns red litmus blue.
CaO(s) + H2O (l) + Ca(OH2)(aq)

Question 31.
A magnesium ribbon is burnt in oxygen to give a white compound X accompanied by emission of light. If the burning ribbon is now placed in an atmosphere of nitrogen, it continues to burn and forms a compound Y.
(i) Write the chemical formulae of X and Y.
(ii) Write the balanced chemical equation when X is dissolved in water.
Answer:
2Mg + O2 → 2MgO + Light
3Mg + N2 → Mg Ni
(i) X is MgO Y is Mg3 N2
(ii) MgO + H2O → Mg(OH)2

Question 32.
Identify the type of reaction in the following examples :
(i) Na2 SO4 (aq) + BaCl2 (aq) → BaSO4(s) + NaCl (aq)
(ii) Fe (8) + CuSO4 (aq) → FeSO4 (aq) + Cu (s)
(iii) 2H2 (g) + O2(g) 2H2O(l)
Answer:
(i) Double displacement reaction,
(ii) Displacement reaction,
(iii) Combination reaction.

Question 33.
During the reaction of some metals with dilute hydrochloric acid, following observations were made :
(i) Silver metal does not show any change.
(ii) The temperature of the reaction mixture rises when aluminium (Al) is added.
(iii) The reaction of sodium metal is found to be highly explosive.
(iv) Some bubbles of a gas are seen when lead (Pb) is reacted with the acid.
Explain these observations giving suitable reasons.
Answer:
(i) Silver being a less reactive metal than hydrogen does not displace hydrogen from HCI. Hence, it does not react with dilute HCI.
(ii) The temperature of the reaction mixture rises when aluminium is added because it is an exothermic reaction.
(iii) Reaction of sodium metal is found to be highly explosive because it is an exothermic reaction.
(iv) When lead is treated with hydrochloric acid, bubbles of hydrogen gas are evolved.
Pb(s) + 2HCl (aq) → PbCl2(aq) + H2(g)

Question 34.
A silver article generally turns black when kept in the open for a few days. The article when rubbed with toothpaste again stars shining.
(a) Why do silver articles turn black when kept in the open for a few days ? Name the phenomenon involved.
(b) Name the black substance formed and give its chemical formula. .
Answer:
(a) Metals such as silver when attacked by substances around it such as moisture, acids, gases etc., are said to corrode and this phenomenon is called corrosion.
(b) The black substance is formed because silver (Ag) reacts with H2S present in air. It forms thin black coating of silver sulphide (Ag2S).

Chemical Reactions and Equations Extra Questions Long Answer Type

Question 1.
Consider the chemical equation given below and answer the questions that follow:

(i) Name the substance which is getting oxidised.
(ii) Name the substance which is getting reduced.
(iii) Name the oxidising agent.
(iv) Name the reducing agent.
(v) What type of a reaction does this equation represent ?
Answer:
(i) The substance getting oxidised is H2
(ii) The substance getting reduced is CuO.
(iii) CuO is the oxidising agent.
(iv) H2 is the reducing agent.
(v) Since oxidation and reduction is taking place simultaneously, this reaction is an example of redox reaction.

Question 2.
Give the characteristic tests for the following gases:
(i) CO2
(ii) SO2
(iii) O2
(iv) H2
Answer:
The characteristic test for
(i) Carbon dioxide (CO2) gas turns lime water milky when passed through it due to the formation of insoluble calcium carbonate.

When CO2 gas is passed in excess through lime water, milkiness disappears due to formation of soluble calcium hydrogen carbonate.

(ii) Sulphur dioxide (SO2) gas when passed through acidic potassium permanganate solution (purple in colour) turns it colourless because SO2 is a strong reducing agent.

(iii) The evolution of oxygen (O2) gas during a reaction can be confirmed by bringing a burning candle near the mouth of the test tube containing the reaction mixture. The intensity of the flame increases because oxygen supports burning.
(iv) Hydrogen (H2 gas burns with a pop sound when a burning candle is brought near it.

Question 3.
With the help of an activity explain that hydrogen and oxygen are released when an electric current is passed through water.
Answer:

(i) Take a plastic vessel. Drill two holes at its bottom and set rubber stoppers in these holes.
(ii) Insert carbon electrodes in these rubber Plastic mug stoppers and connect these electrodes to a 6 volt battery and a switch.
(iii) Fill the vessel with water such that the electrodes are immersed. Add a few drops Test tube wenn of dilute sulphuric acid to the water in the nows Water vessel.
(iv) Take two graduated test tubes filled Water with water and invert them over the two carbon electrodes.
(v) Switch on the current.
(vi) After sometime, you will observe the formation of bubbles at both the electrodes. These bubbles displace water in the graduated tubes.
(vii) Once the test tubes are filled with the respective gases, remove them carefully.
(viii) Test these gases one by one by bringing a burning splinter of wood close to the mouth of test tubes.

When the glowing splinter of wood is brought close to the mouth of one test tube, it relights and when it is brought close to the mouth of other test tube, the gas burns with a pop. Oxygen is the only common gas that relights the splinter and hydrogen gas burns with a pop.

Question 4.
What happens when a piece of:
(a) zinc metal is added to copper sulphate solution ?
(b) aluminium metal is added to dilute hydrochloric acid ?
(c) silver metal is added to copper sulphate solution ? Also, write the balanced chemical equation if the reaction occurs.
Answer:
(a) Zinc being more reactive than copper displaces copper from its solution and a solution of zinc sulphate is obtained.

(b) Aluminium being more reactive displaces hydrogen from dilute hydrochloric acid solution and hydrogen gas is evolved.

(c) Silver metal being less reactive than copper cannot displace copper from its salt solution. Therefore, no reaction occurs.
Ag(s) + CuSO4 (aq) → No reaction

Question 5.
What happens when zinc granules are treated with dilute solution of H2SO4, HCI, HNO2, NaCl and NaOH ? Also write the chemical equations if reaction occurs.
Answer:
The reaction of Zn granules with
(i) dilute H2SO4
Zn(s) + H2SO4 (aq) → ZnSO4(aq) + H2(g)
(ii) dilute HCI
Zn(s) + 2HCl (aq) → ZnCl2(aq) + H2 (g)
(iii) dilute HNO,
Reaction with dilute HNO, is different as compared to other acids because nitric acid is an oxidising agent and it oxidises H2 gas evolved to H2O.
4Zn(s) + 10HNO2 (aq) + 4Zn(NO3)2(aq) + 5H2O (l) +N2O (g)
(iv) NaCl solution
Zn(s) + NaCl(aq) → No reaction
(v) NaOH solution

Question 6.
What happens when : (Give chemical reactions only)
(i) Ferrous sulphate is heated.
(ii) Sodium metal reacts with water.
Answer:

(ii) 2Na(s) + 2H4O(l) → 2NaOH(aq)

Question 7.
Balance the following chemical reactions :
(i) CO2 + H2O → C6H12O6 + O2 + H2O.

Answer:
(i) 6CO2 + 12H2O → C6H12O6 + 6O2 +6H2O


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