Chemical Reactions & Equations

Question 1

The reaction of ‘magnesium’ with air is

Accepted Answer

Exothermic reaction

Answer

Endothermic reaction

Answer

Reversible reaction

Answer

Substitution reaction

Question 2

Magnesium ribbon is rubbed before burning because it has a coating of

Accepted Answer

basic magnesium carbonate

Answer

basic magnesium oxide

Answer

basic magnesium sulphide

Answer

basic magnesium chloride

Question 3

What chemicals are used in fireworks?

Accepted Answer

All of above

Answer

Copper chloride

Answer

Calcium chloride

Answer

Barium chloride

Question 4

The chemical formula of lead sulphate is

Accepted Answer

PbSO4

Answer

Pb2SO4

Answer

Pb(SO4)2

Answer

Pb2(SO4)3

Question 5

When a magnesium ribbon is burnt in the air, the ash formed is

Accepted Answer

White

Answer

Black

Answer

Yellow

Answer

Pink

Question 6

Which information is not conveyed by a balanced chemical equation?

Accepted Answer

Whether a particular reaction is actually feasible or not

Answer

Physical states of reactants and products

Answer

Symbols and formulae of all the substances involved in a particular reaction

Answer

Number of atoms/molecules of the reactants and products formed

Question 7

The color of magnesium oxide is

Accepted Answer

White

Answer

Blue

Answer

Grey

Answer

Pink

Question 8

Chemically rust is

Accepted Answer

hydrated ferric oxide

Answer

hydrated ferrous oxide

Answer

only ferric oxide

Answer

none of these

Question 9

When carbon dioxide is passed through lime water,

Accepted Answer

Lime water turns milky

Answer

Calcium hydroxide is formed

Answer

A white precipitate of CaO is formed

Answer

Color of lime water disappears.

Question 10

Both CO2 and H2 gases are

Accepted Answer

colorless

Answer

heavier than air

Answer

acidic in nature

Answer

soluble in water

Question 11

When crystals of lead nitrate are heated strongly in a dry test tube

Accepted Answer

A brown residue is left

Answer

Crystals immediately melt

Answer

White fumes appear in the tube

Answer

A yellow residue is left

Question 12

Which of the following gases can be used for the storage of fresh samples of oil for a long time?

Accepted Answer

Nitrogen or helium

Answer

Carbon dioxide or oxygen

Answer

Helium or oxygen

Answer

Nitrogen or oxygen

Question 13

Consider equations: Ca⁺²(aq) + 2OH‾(aq)→Ca(OH)₂ (s). The precipitate of calcium hydroxide will be of

Accepted Answer

White color

Answer

Green color

Answer

Blue color

Answer

Brown color

Question 14

In writing chemical equations, the inclusion of state symbols shall be done while

Accepted Answer

The equation has been balanced

Answer

Correct chemical formulae of reactants and products are written

Answer

The equation is being balanced to fulfill the law of conservation of mass

Answer

The chemical formulae of products and reactants have been changed to bring about quick balancing

Question 15

The electrolytic decomposition of water gives H2 and O2 in the ratio of

Accepted Answer

2: 1 by volume

Answer

1: 2 by volume

Answer

8: 1 by mass

Answer

1: 2 by mass

Question 16

Consider the equation: Pb⁺² (aq) + 2OH⁻ (aq) → Pb(OH)₂ (s), the precipitate of lead (II) hydroxide will be of

Accepted Answer

White color

Answer

Green color

Answer

Blue color

Answer

Brown color

Question 17

Consider the equation: Cu⁺² (aq) + 2OH⁻(aq) → Cu(OH)₂ (s), the precipitate of Copper Hydroxide (Cu(OH)₂) will be of

Accepted Answer

Blue color

Answer

Green color

Answer

Brown color

Answer

White color

Question 18

In the decomposition of lead (II) nitrate to give lead (II) oxide, nitrogen dioxide, and oxygen gas, the coefficient of nitrogen dioxide (in the balanced equation) is

Accepted Answer

4

Answer

1

Answer

2

Answer

3

Question 19

Consider reaction: Na(s) + O₂(g) → Na₂O(s). Moles of sodium needed to balance equation would be

Accepted Answer

4

Answer

1

Answer

2

Answer

3

Question 20

Consider the reaction: S(s) + O₂(g) → SO₂. The state of SO₂ in this reaction is

Accepted Answer

Gaseous

Answer

Liquid

Answer

Solid

Answer

All Three

Question 21

Fatty foods become rancid due to the process of

Accepted Answer

oxidation

Answer

corrosion

Answer

reduction

Answer

hydrogenation

Question 22

Consider reaction: P(s) + O₂(g) → P₄O₁₀(s). Moles of O₂(g) needed to balance the equation will be

Accepted Answer

5

Answer

1

Answer

3

Answer

7

Question 23

We store silver chloride in a dark-colored bottle because it is

Accepted Answer

to avoid action by sunlight

Answer

a white solid

Answer

undergoes redox reaction

Answer

None of the above

Question 24

Consider reaction: Al(s) + O₂ (g) → Al₂O₃. Moles of Al(s) needed to balance equation are

Accepted Answer

4

Answer

1

Answer

2

Answer

3

Question 25

Which one of the given processes involves chemical reactions?

Accepted Answer

Heating copper wire in the presence of air at high temperature

Answer

Storing of oxygen gas under pressure in a gas cylinder

Answer

Keeping petrol in a China dish in the open

Answer

Liquefaction of air

Question 26

In which of the given chemical equations, the abbreviations represent the correct states of the reactants and products involved at reaction temperature?

Accepted Answer

2H₂ (g) + O₂ (g) → 2H₂O (l)

Answer

2H₂ (l) + O₂ (l) → 2H₂O (g)

Answer

2H₂ (g) + O₂ (l) → 2H₂O (g)

Answer

2H₂ (g) + O₂ (g) → 2H₂O (g)

Question 27

The silver article turns black when kept in the open for a few days due to the formation of

Accepted Answer

Ag2S

Answer

H2S

Answer

AgS

Answer

AgSO4

Question 28

The reaction in which two compounds exchange their ions to form two new compounds is called

Accepted Answer

Double displacement reaction

Answer

Displacement reaction

Answer

Combination reaction

Answer

Redox reaction

Question 29

Which of the given gases can be used for the storage of fresh samples of oil for a long time?

Accepted Answer

Nitrogen or helium

Answer

Carbon dioxide or oxygen

Answer

Helium or oxygen

Answer

Nitrogen or oxygen

Question 30

An element X on exposure to moist air turns reddish-brown and a new compound Y is formed. The substance X and Y are

Accepted Answer

X = Fe, Y = Fe2O3

Answer

X = Ag, Y = Ag2S

Answer

X = Cu, Y = CuO

Answer

X = Al, Y = Al2O3

Question 31

Which of the following are exothermic processes?

Accepted Answer

Reaction of water with quick lime

Answer

Dilution of an acid

Answer

Evaporation of water

Answer

Sublimation of camphor (crystals)

Question 32

On immersing an iron nail in CuSO4 solution for few minutes, you will observe

Accepted Answer

the color of the solution changes to green

Answer

no reaction takes place

Answer

the color of the solution fades away

Answer

the surface of iron nails acquire a black coating

Question 33

Rancidity can be prevented by

Accepted Answer

all of these

Answer

adding antioxidants

Answer

storing food away from light

Answer

keeping food in the refrigerator

Question 34

In which of the following, heat energy will be evolved?

Accepted Answer

Burning of L.P.G.

Answer

Electrolysis of water

Answer

Dissolution of NH4Cl in water

Answer

Decomposition of AgBr in the presence of sunlight

Question 35

Which of the following statements about the given reaction are correct? 3Fe(s) + 4H₂O(g) → Fe₃O₄ (s) + 4H₂ (g)

Accepted Answer

Water is acting as reducing agent.

Answer

Iron metal is getting oxidized.

Answer

Water is getting reduced.

Answer

Water is acting as oxidizing agent.

Question 36

A dilute ferrous sulphate solution was gradually added to the beaker containing acidified permanganate solution. The light purple color of the solution fades and finally disappears. Which of the given equation is the correct explanation for the observation?

Accepted Answer

KMnO₄ is an oxidizing agent, it oxidizes FeSO₄

Answer

FeSO₄ acts as an oxidizing agent and oxidizes KMnO₄

Answer

The color disappears due to dilution, no reaction is involved

Answer

KMnO₄ is an unstable compound and decomposes in the presence of FeSO₄ to a colorless compound

Question 37

A teacher gave two test tubes to the students, one containing water and the other containing sodium hydroxide. She asked them to identify the test tube containing sodium hydroxide solution. Which one of the following can be used for identification?

Accepted Answer

Red litmus

Answer

Blue litmus

Answer

Sodium carbonate solution

Answer

Dilute hydrochloric acid

Question 38

Magnesium ribbon is rubbed before burning because it has a coating of

Accepted Answer

basic magnesium carbonate

Answer

basic magnesium oxide

Answer

basic magnesium sulphide

Answer

basic magnesium chloride

Question 39

Which of the following is not a physical change?

Accepted Answer

Combustion of Liquefied Petroleum Gas (LPG)

Answer

Boiling of water to give water vapor

Answer

Melting of ice to give water

Answer

Dissolution of salt in water

Question 40

Which of the following statements about the given reaction are correct? 3Fe (s) + 4H2O (g) → Fe3O4 (s) + 4 H2 (g)
(i) Iron metal is getting oxidised
(ii) Water is getting reduced
(iii) Water is acting as reducing agent
(iv) Water is acting as oxidising agent

Accepted Answer

Water is acting as reducing agent

Answer

Iron metal is getting oxidised

Answer

Water is getting reduced

Answer

Water is acting as oxidising agent

Answer

(i), (zi) and (iii)

Answer

(in) and (iv)

Answer

(i), (ii) and (iv)

Answer

(ii) and (iv)

Question 41

In which of the following chemical equations, the abbreviations represent the correct states of the reactants and products involved at reaction temperature?

Accepted Answer

2H2 (g) +O2 (g) > 2H2O (g)

Answer

2H2 (l) + O2 (l) > 2H2O(g)

Answer

2H2 (g) + O2 (l) > 2H2O (l)

Answer

2H2 (g) + O2 (g) > 2H2O (l)

Question 42

In the double displacement reaction between aqueous potassium iodide and aqueous lead nitrate, a yellow precipitate of lead iodide is formed. While performing the activity if lead nitrate is not available, which of the following can be used in place of lead nitrate?

Accepted Answer

Lead acetate

Answer

Lead sulphate (insoluble)

Answer

Ammonium nitrate

Answer

Potassium sulphate

Question 43

A dilute ferrous sulphate solution was gradu¬ally added to the beaker containing acidified permanganate solution. The light purple color of the solution fades and finally disap¬pears. Which of the following is the correct explanation for the observation?

Accepted Answer

KMnO4 is an oxidizing agent, it oxidizes FeSO4.

Answer

FeSO4 acts as an oxidizing agent and oxidizes KMNO4.

Answer

The color disappears due to dilution; no reaction is involved.

Answer

KMnO4 is an unstable compound and decomposes in presence of FeSO4. to a colorless compound.

Question 44

Barium chloride on reacting with ammonium sulphate forms barium sulphate and ammonium chloride. Which of the following correctly represents the type of reaction involved?
(i) Displacement reaction
(ii) Precipitation reaction
(iii) Combination reaction
(iv) Double displacement reaction

Accepted Answer

Double displacement reaction

Answer

Displacement reaction

Answer

Precipitation reaction

Answer

Combination reaction

Answer

(i) only

Answer

(ii) only

Answer

(iv) only

Answer

(ii) and (iv)

Question 45

Pb + CuCl2 → PbCl2 + Cu. The above reaction is an example of:

Accepted Answer

displacement

Answer

combination

Answer

double displacement

Answer

decomposition

Question 46

Combustion reactions are always

Accepted Answer

Exothermic

Answer

Endothermic

Answer

Sometimes exothermic

Answer

Both (a) and (b).

Question 47

Which of the following is Not True with respect to the neutralization reaction?

Accepted Answer

Reactants are in a gaseous state.

Answer

Salt is formed.

Answer

Reaction occurs between an acid and a base.

Answer

Reactive element displaces less reactive element.

Question 48

Name the products formed when iron filings are heated with dilute hydrochloric acid

Accepted Answer

Fe (II) chloride and hydrogen gas

Answer

Fe (III) chloride and water

Answer

Fe (II) chloride and water

Answer

Fe (III) chloride and hydrogen gas

Question 49

The following reaction is used for the preparation of oxygen gas in the laboratory: 2KClO₃ (s) → 2KCl (s) + 3O₂ (g) Which of the following statement about the reaction is correct?

Accepted Answer

It is a decomposition reaction and endothermic in nature.

Answer

It is a combination reaction.

Answer

It is a decomposition reaction and accompanied by the release of heat.

Answer

It is a photochemical decomposition reaction and exothermic in nature.

Question 50

The condition produced by aerial oxidation of fats and oils in foods marked by unpleasant smell and taste is called:

Accepted Answer

rancidity

Answer

antioxidation

Answer

reduction

Answer

corrosion

Question 51

A substance added to food containing fats and oils is called:

Accepted Answer

Antioxidant

Answer

Oxidant

Answer

Rancid

Answer

Coolant

Question 52

Select the oxidising agent for the following reaction: H2S + I2 > 2HI + S

Accepted Answer

I2

Answer

H2S

Answer

HI

Answer

S

Question 53

What type of chemical reactions takes place when electricity is passed through water?

Accepted Answer

Decomposition

Answer

Displacement

Answer

Combination

Answer

Double displacement

Question 54

In the double displacement reaction between aqueous potassium iodide and aqueous lead nitrate, a yellow precipitate of lead iodide is formed. While performing the activity if lead nitrate is not available, which of the following can be used in place of lead nitrate?

Accepted Answer

Lead acetate

Answer

Lead sulphate (insoluble)

Answer

Ammonium nitrate

Answer

Potassium sulphate

Question 55

When Ag is exposed to air it gets a black coating of

Accepted Answer

Ag2S

Answer

AgNO3

Answer

Ag2O

Answer

Ag2CO3

Question 56

A substance ‘X’ is used in white-washing and is obtained by heating limestone in the absence of air. Identify ‘X’.

Accepted Answer

CaO

Answer

CaOCl2

Answer

Ca (OH)2

Answer

CaCO3

Question 57

The process of reduction involves

Accepted Answer

addition of hydrogen

Answer

addition of oxygen

Answer

removal of oxygen

Answer

removal of hydrogen

Question 58

Which of the following are exothermic processes?
(i) Reaction of water with quick lime
(ii) Dilution of an acid
(iii) Evaporation of water
(iv) Sublimation of camphor (crystals)

Accepted Answer

Reaction of water with quick lime

Answer

Dilution of an acid

Answer

Evaporation of water

Answer

Sublimation of camphor (crystals)

Answer

(i) and (ii)

Answer

(ii) and (iii)

Answer

(i) and (iv)

Answer

(ii) and (iv)

Question 59

Before burning in air, the magnesium ribbon is cleaned by rubbing with sandpaper to:

Accepted Answer

Remove the layer of magnesium oxide from the ribbon surface

Answer

Make the ribbon surface shinier

Answer

Remove the layer of magnesium carbonate from the ribbon surface

Answer

Remove the moisture from the ribbon surface

Question 60

In a chemical reaction between sulphuric acid and barium chloride solution the white precipitates formed are of:

Accepted Answer

Barium sulphate

Answer

Hydrochloric acid

Answer

Chlorine

Answer

Sulphur

Question 61

The respiration process during which glucose undergoes slow combustion by combining with oxygen in the cells of our body to produce energy is a kind of:

Accepted Answer

Exothermic process

Answer

Endothermic process

Answer

Reversible process

Answer

Physical process

Question 62

A chemical reaction does not involve:

Accepted Answer

Changing of the atoms of one element into those of another element to form new products

Answer

Formation of new substances having entirely different properties than that of the reactants

Answer

Breaking of old chemical bonds and formation of new chemical bonds

Answer

Rearrangement of the atoms of reactants to form new products

Question 63

One of the following processes does not involve a chemical reaction. That is:

Accepted Answer

Melting of candle wax when heated

Answer

Burning of candle wax when heated

Answer

Digestion of food in our stomach

Answer

Ripening of banana

Question 64

It is necessary to balance a chemical equation in order to satisfy the law of:

Accepted Answer

Conservation of mass

Answer

Conservation of motion

Answer

Conservation of momentum

Answer

Conservation of energy

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