CBSE Class 10 Chemistry Chemical Reaction and Equations Worksheet Set A

Chemical Reactions and Equations Assertion Reason Class 10 Science

A. Both assertionand reason are true, and reason is the correct explanation of assertion.
B. Both assertion and reason are true, but reason is not the correct explanation of assertion.
C. Assertion is true but reason is false.
D. Assertion is false and reason is true.

Question. Assertion(A): Sulphur dioxide and Sulphur trioxides are released during the decomposition of iron sulphate.
Reason(R): This is an example of thermal decomposition.

Answer: B

Question. Assertion(A): Brown fumes are obtained from the thermal decomposition of Lead Nitrate.
Reason(R): Nitrogen dioxide gas is released which is brown in colour.

Answer: A

Question. Assertion(A): Acidification of water decreases its conductivity during electrolysis.
Reason(R): H+ ions are released which hinder the flow of charges.

Answer: D

Question. Assertion(A): After white washing the walls, a shiny white finish on walls is obtained after three or four days.
Reason(R): Calcium hydroxide reacts with Carbon dioxide to form Calcium Carbonate which gives shiny white finish.

Answer: A

Question. Assertion(A): The glucose combines with oxygen in the cells of our body and provides energy.
Reason(R): Respiration is an example of oxidation reaction.

Answer: B

Question. Assertion(A): Silver Bromide is used in black and white photography.
Reason(R): Silver Bromide decomposes in the presence of sunlight.

Answer: B

Question. Assertion(A): In double displacement reactions, no precipitate is formed.
Reason(R): Barium Sulphate is precipitated during the double displacement reaction between Sodium Sulphate and Barium Chloride.

Answer: D

Question. Assertion(A): The surface of copper powder becomes black on heating.
Reason: Black colour copper oxide is formed.

Answer: A

Question : A silver article generally turns black when kept in the open for a few days. The article when rubbed with toothpaste again starts shining. a. Why do silver articles turn black when kept in the open for a few days? Name the phenomenon involved Name the black substance formed and give its chemical formula.
Answer :  A The metal surface of silver articles reacts with atmospheric sulphur compounds like hydrogen sulphide and forms black layer of sulphides. This phenomenon is called as corrosion or tarnishing of silver. (B) The black substance that is formed by the reaction of hydrogen sulphide and atmospheric oxygen is silver sulphide
(Ag₂S). 4Ag + O₂ + 2H₂S → 2Ag₂S + 2H₂O

Question : P, Q and R are 3 elements which undergo chemical reactions according to the following equations:
(i) P₂O₃ + 2Q → Q₂O₃ + 2P
(ii) 3RSO₄ + 2Q → Q₂(SO₄)₃ + 3R
(iii) 3RO + 2P → P₂O₃ + 3R
Answer the following:
(A) Which element is most reactive?
(B) Which element is least reactive?
(C) State the type of reaction listed above.
Answer : Element Q displaces P and R from their compounds in reaction ‘a’ and reaction ‘b’ respectively. So element Q is more reactive than P and R. Also element P displaces element R in reaction ‘c’. So we can say that
(A) Q is the most reactive element
(B) R is the least reactive element.
(C) The above reactions are displacement reactions.

Question : No chemical reaction takes place when granules of a solid A are mixed with the powder of another solid B. However when the mixture is heated, a reaction takes place between its components. One of the products, C, is a metal and settles down in its molten state, while the other product, D, floats over it. It was observed that the reaction is highly exothermic
(1) Based on the given information, make an assumption about A and B and write a chemical equation for the chemical reaction indicating the conditions of the reaction, physical state of reactions and products and thermal status of reaction.
(2) Mention any two types of reaction under which the above chemical reaction can be classified
Answer :  Here, A is solid manganese granules while B is aluminium powder. When they are mixed ogether, no reaction takes place. However, on heating, thermite reaction takes place. Here, the aluminium takes the oxygen from the manganese dioxide to form molten metallic manganese. It also results in the formation of aluminium oxide which floats over manganese metal. The chemical reaction is as follows: 
3MnO₂(s) + 4Al(s) Δ→ 3Mn(l) + 2Al₂O₃(s)
Manganese Aluminium Metal Aluminium
dioxide manganese oxide

 

Question : A solution of potassium chloride when mixed with silver nitrate solution forms an insoluble white substance. Write the chemical reaction involved and also mention the type of the chemical reaction.
Answer :  When a solution of potassium chloride is mixed with silver nitrate solution, we get a precipitate of silver chloride. Chlorides are usually soluble but one important exception to this rule is silver chloride. The chemical reaction is:
KCl + AgNO₃ → KNO₃(aq) + AgCl(s) This type of chemical reaction is called a double displacement reaction.

Question : 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) The decomposition of ferrous sulphate absorbs heat during reaction. Therefore, it is an example of endothermic reaction.
(B) When we dissolve sulphuric acid in water, a large amount of heat is liberated, so it is an exothermic reaction.
(C) When we dissolve sodium hydroxide in water, a large amount of heat is liberated, so it is an exothermic reaction.
(D) The mixing of ammonium chloride in water absorbs heat from the reaction mixture. Therefore, it is an example of endothermic reaction.

Question : 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) The decomposition of ferrous sulphate absorbs heat during reaction. Therefore, it is an example of endothermic reaction.
(B) When we dissolve sulphuric acid in water, a large amount of heat is liberated, so it is an exothermic reaction.
(C) When we dissolve sodium hydroxide in water, a large amount of heat is liberated, so it is an exothermic reaction.
(D) The mixing of ammonium chloride in water absorbs heat from the reaction mixture. Therefore, it is an example of endothermic reaction.  

Question : Convert the following word equations to balanced chemical equations. 

i. Hydrogen gas combines with nitrogen to from ammonia

ii. Hydrogen sulphide gas burns in air to give water and sulphur dioxide.

iii. Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.

iv. Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.

v. Hydrogen sulphide gas reacts with oxygen gas to form solid sulphur and liquid water.

Answer :

 

Question : Write three equations for decomposition reaction where energy is supplied in the form of heat, light and electricity? 

Answer :