1. Chemical Reactions and Equations

SEBA Class 10 Science Chapter 1. Chemical Reactions and Equations

Chapter 1. Chemical Reactions and Equations

Class 10 Science Multiple Choice Questions

Question : Which of the statements about the reaction below are incorrect?
2PbO(s)+C(s) → 2Pb(s)+CO2(g)
(a) Lead is getting reduced.
(b) Carbon dioxide is getting oxidised.
(c) Carbon is getting oxidised.
(d) Lead oxide is getting reduced.
(i) (a) and (b)
(ii) (a) and (c)
(iii) (a), (b) and (c)
(iv) all

Answer : (i) (a) and (b)
Question :
The above reaction is an example of a [SEBA 2016,2018]
(a) combination reaction.
(b) double displacement reaction
(c) decomposition reaction.
(d) displacement reaction.

Answer : (d) displacement reaction.
Question : What happens when dilute hydrochloric acid is added to iron fillings? Tick the correct answer. [SEBA 2017]
(a) Hydrogen gas and iron chloride are produced.
(b) Chlorine gas and iron hydroxide are produced.
(c) No reaction takes place.
(d) Iron salt and water are produced.

Answer : (a) Hydrogen gas and iron chloride are produced.

Question: Which of the following metals can replace copper from a solution of copper sulphate ? [SEBA 2015]

(a) Silver (b) Gold (c) Zinc (d) Mercury

Answer : (c) Zinc

[ Zinc is more reactive than copper. Therefore, zinc can replace copper from a solution of copper sulphate. ]

Question : Decomposition of vegetable matters into compost in an example of which of the following class of reaction ? [SEBA 2023]

(a) Endothermic (b) Exothermic reaction (c) Both (d) None of the above

Answer : (b) Exothermic reaction

[The decomposition of vegetable matter into compost is an example of an exothermic reaction.]

Question : The product ‘X’ of the following reaction is . [SEBA 2023]

Answer :

Given, the balance chemical reaction is ]

Question : Which of the following is not a physical change?

(a) Boiling of water to give water vapour

(b) Melting of ice to give water

(d) Combustion of Liquefied Petroleum Gas (LPG)

Answer : (d) Combustion of Liquefied Petroleum Gas (LPG)

[ Combustion is a chemical change, not a physical change. In the case of Liquefied Petroleum Gas (LPG) combustion, it produces carbon dioxide, water vapor, and heat, which are different substances compared to the original LPG. Physical changes, on the other hand, involve changes in the physical state or appearance of a substance without the formation of new substances. ]

Question : The following reaction is an example of a

(i) displacement reaction

(ii) combination reaction

(iii) redox reaction

(iv) neutralisation reaction

(a) (i) and (iv) (b) (ii) and (iii) (c) (i) and (iii) (d) (iii) and (iv)

Answer : (c) (i) and (iii)

[ The given reaction: is an example of a redox reaction .]

Question : Which of the following statements about the given reaction are correct?

(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

(a) (i), (ii) and (iii) (b) (iii) and (iv)

Answer : (c) (i), (ii), and (iv)

[ The given reaction:

This means that iron is oxidized, water is reduced, and water also acts as an oxidizing agent in the given reaction. ]

Question : 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)

(a) (i) and (ii) (b) (ii) and (iii)

Answer : (a) (i) and (ii).

[ Explanation: (i) This is an exothermic process because it releases heat when calcium oxide (quicklime) reacts with water to form calcium hydroxide (slaked lime).

(ii) Diluting an acid is an exothermic process. When an acid is mixed with water, it releases heat to the surroundings.

So, the only exothermic processes among the given options are (i) and (ii). ]

Question : Three beakers labelled as A, B and C each containing 25 mL of water were taken. A small amount of NaOH, anhydrous CuSO4 and NaCl were added to the beakers A, B and C respectively. It was observed that there was an increase in the temperature of the solutions contained in beakers A and B, whereas in case of beaker C, the temperature of the solution falls. Which one of the following statement(s) is(are) correct?

(i) In beakers A and B, exothermic process has occurred.

(ii) In beakers A and B, endothermic process has occurred.

(iii) In beaker C exothermic process has occurred.

(iv) In beaker C endothermic process has occurred.

(a) (i) only (b) (ii) only

Answer : (c) (i) and (iv)

[ Explanation : In beaker A, NaOH is added to water, and the dissolution of NaOH in water is an exothermic process. It releases heat to the surroundings, causing the temperature to increase.

In beaker B, anhydrous CuSO4 is added to water, and the dissolution of anhydrous CuSO4 in water is also an exothermic process. It releases heat to the surroundings, leading to a temperature increase.

In beaker C, NaCl is added to water, and the dissolution of NaCl in water is an endothermic process. It absorbs heat from the surroundings, causing the temperature to decrease.

Therefore, statements (i) and (iv) are correct, indicating that exothermic processes occurred in beakers A and B, while an endothermic process occurred in beaker C. ]

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

(a) is an oxidising agent, it oxidises

(b) acts as an oxidising agent and oxidises

(d) is an unstable compound and decomposes in presence of to a colourless compound.

Answer : (a) is an oxidizing agent; it oxidizes .

[ Explanation: Potassium permanganate () is a strong oxidizing agent. Ferrous sulphate () is a reducing agent.

When ferrous sulphate is added to acidified potassium permanganate solution, the manganese in undergoes reduction, resulting in the formation of colorless manganese ions.

The purple color of the permanganate solution fades and finally disappears because the manganese ions formed are colorless.

Therefore, the correct explanation is that is an oxidizing agent, and it oxidizes . The reaction involves the reduction of and the oxidation of . ]

Question : Which among the following is(are) double displacement reaction(s)?

(i)

(ii)

(iii)

(iv)

(a) (i) and (iv) (b) (ii) only

Answer : (b) (ii) only

[ Explanation : In a double displacement reaction, the positive and negative ions of two ionic compounds exchange places to form two new compounds.

In option (ii), is a double displacement reaction. and NaCl are the products formed by the exchange of ions. ]

Question : Which among the following statement(s) is(are) true? Exposure of silver chloride to sunlight for a long duration turns grey due to

(i) the formation of silver by decomposition of silver chloride

(ii) sublimation of silver chloride

(iii) decomposition of chlorine gas from silver chloride

(iv) oxidation of silver chloride

(a) (i) only (b) (i) and (iii)

Answer : (a) (i) only

[ Explanation: Exposure of silver chloride (AgCl) to sunlight for a long duration causes it to turn grey due to the decomposition of silver chloride.

Sunlight provides energy to break the chemical bonds in silver chloride, leading to the release of silver and chlorine gas.

The decomposition reaction is :

Therefore, statement (i) is true. ]

Question : Solid calcium oxide reacts vigorously with water to form calcium hydroxide accompanied by liberation of heat. This process is called slaking of lime. Calcium hydroxide dissolves in water to form its solution called lime water. Which among the following is (are) true about slaking of lime and the solution formed?

(i) It is an endothermic reaction

(ii) It is an exothermic reaction

(iii) The pH of the resulting solution will be more than seven

(iv) The pH of the resulting solution will be less than seven

(a) (i) and (ii) (b) (ii) and (iii)

Answer : (b) (ii) and (iii)

[ Explanation: The slaking of lime is an exothermic reaction because it releases heat when solid calcium oxide reacts with water to form calcium hydroxide.

The resulting solution, lime water dissolved in water), is basic. When calcium hydroxide dissolves in water, it forms hydroxide ions() , making the solution alkaline.Therefore, the pH of the resulting solution will be more than seven. ]

Question : Barium chloride on reacting with ammonium sulphate forms barium sulphate and ammonium chloride. Which of the following correctly represents the type of the reaction involved?

(i) Displacement reaction

(ii) Precipitation reaction

(iii) Combination reaction

(iv) Double displacement reaction

(a) (i) only (b) (ii) only

Answer : (d) (ii) and (iv)

[ Explanation: In the given reaction

This is a double displacement reaction (iv) because the positive and negative ions from two different compounds exchange places to form two new compounds.

Additionally, it is also a precipitation reaction (ii) because the formation of barium sulfate results in the precipitation of a solid (barium sulphate) from the solution. ]

Question : Electrolysis of water is a decomposition reaction. The mole ratio of hydrogen and oxygen gases liberated during electrolysis of water is

(a) 1:1

(b) 2:1

(d) 1:2

Answer : The correct answer is (b) 2:1.

[ Explanation:

For every two moles of water molecules, one mole of oxygen gas and two moles of hydrogen gas are produced. Therefore, the mole ratio of hydrogen to oxygen is 2:1. ]

Question : Which of the following is(are) an endothermic process(es)?

(i) Dilution of sulphuric acid

(ii) Sublimation of dry ice

(iii) Condensation of water vapours

(iv) Evaporation of water

(a) (i) and (iii) (b) (ii) only

Answer : (d) (ii) Sublimation of dry ice and (iv) Evaporation of water

[ Explanation: Sublimation of dry ice () involves the transition from a solid to a gas, which typically requires an input of energy.

Evaporation of water involves the phase transition from a liquid to a gas, and this process absorbs heat. ]

Question : 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?

(a) Lead sulphate (insoluble)

(b) Lead acetate

(d) Potassium sulphate

Answer : (b) Lead acetate

[ Explanation : Lead acetate is a soluble salt, and when it reacts with aqueous potassium iodide, it will provide lead ions to form lead iodide as a yellow precipitate. ]

Question : Which of the following gases can be used for storage of fresh sample of an oil for a long time?

(a) Carbon dioxide or oxygen

(b) Nitrogen or oxygen

(d) Helium or nitrogen

Answer : (d) Helium or nitrogen

[ Explanation : Helium and nitrogen are inert gases, and they do not readily react with the oil or contribute to oxidation or degradation. Therefore, using helium or nitrogen is suitable for the long-term storage of a fresh oil sample. ]

Question : The following reaction is used for the preparation of oxygen gas in the laboratory

Which of the following statement(s) is(are) correct about the reaction?

(a) It is a decomposition reaction and endothermic in nature

(b) It is a combination reaction

(d) It is a photochemical decomposition reaction and exothermic in nature

Answer : (a) It is a decomposition reaction and endothermic in nature

[ Explanation:

This is a decomposition reaction as a single substance () breaks down into multiple products (KCl and ). ]

Question : Which one of the following processes involve chemical reactions?

(a) Storing of oxygen gas under pressure in a gas cylinder

(b) Liquefaction of air

(d) Heating copper wire in presence of air at high temperature

Answer : (d) Heating copper wire in the presence of air at high temperature

[ Explanation : When copper wire is heated in the presence of air at high temperatures, it undergoes oxidation, forming copper oxide. ]

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

(a)

(b)

(c)

(d)

Answer : (c)

[ Explanation :

This is indicates that hydrogen gas () and oxygen gas () are in the gaseous state before the reaction, and water () is in the liquid state after the reaction.]

Question : Which of the following are combination reactions?

(i)

(ii)

(iii)

(iv)

(a) (i) and (iii) (b) (iii) and (iv)

Answer : (d) (ii) and (iii)

[ Explanation : (ii) . This is a combination reaction.

(iii) . This is a combination reaction .]