CBSE Class 10 Chemistry Chemical Reactions And Equations Worksheet Set 06

This Class 10 Chemistry worksheet, Set 06, has 18 short questions with answers from Chapter 1, Chemical Reactions and Equations. It is made to be printed and covers physical and chemical changes, balancing, types of reactions, oxidation, corrosion and rancidity.

Short Questions with Answers

Question 1. Which one is a chemical change: rusting of iron or melting of iron?
Answer:
Rusting of iron is a chemical change because a new substance (rust) forms. Melting is only a change of state.
In simple words: New substance means chemical change.

Teacher's Note:
1. Key idea: New substance means chemical change.
2. Write the answer in one clear line.

Question 2. Hydrogen and oxygen combine with each other to form water. Name the reactants and products.
Answer:
Reactants: hydrogen and oxygen. Product: water. 2H₂ + O₂ → 2H₂O
In simple words: Reactants are on the left, products on the right.

Teacher's Note:
1. Key idea: Reactants are on the left, products on the right.
2. Write the answer in one clear line.

Question 3. The molecular formula of chloride of cation X is XCl. What is the formula of nitrate of X?
Answer:
X has valency 1 as it combines with one Cl. The nitrate ion is NO₃⁻, so the nitrate is XNO₃.
In simple words: Same valency, so one nitrate ion per X.

Teacher's Note:
1. Key idea: Same valency, so one nitrate ion per X.
2. Write the answer in one clear line.

Question 4. What is meant by skeletal equation?
Answer:
An unbalanced chemical equation, showing only the formulae of reactants and products, is a skeletal equation. Example: Mg + HCl → MgCl₂ + H₂
In simple words: Skeletal means not yet balanced.

Teacher's Note:
1. Key idea: Skeletal means not yet balanced.
2. Write the answer in one clear line.

Question 5. Complete and balance the following reaction: Fe₂O₃ + Al →
Answer:
Fe₂O₃(s) + 2Al(s) → Al₂O₃(s) + 2Fe(s)
In simple words: Aluminium displaces iron from its oxide.

Teacher's Note:
1. Key idea: Aluminium displaces iron from its oxide.
2. Write the answer in one clear line.

Question 6. Balance the following chemical equation: FeSO₄(s) →^heat Fe₂O₃(s) + SO₂(g) + SO₃(g)
Answer:
2FeSO₄(s) →^heat Fe₂O₃(s) + SO₂(g) + SO₃(g)
Check: Fe 2 = 2; S 2 = 2; O 8 = 3 + 2 + 3 = 8.
In simple words: Two FeSO₄ are needed to make one Fe₂O₃.

Teacher's Note:
1. Key idea: Two FeSO₄ are needed to make one Fe₂O₃.
2. Write the answer in one clear line.

Question 7. Name the reaction in which two substances react to form a new substance.
Answer:
A combination reaction.
In simple words: Two or more substances join to give one product.

Teacher's Note:
1. Key idea: Two or more substances join to give one product.
2. Write the answer in one clear line.

Question 8. What type of reaction occurs in the digestion of food in our body?
Answer:
Digestion breaks big molecules into simpler ones, so it is a decomposition reaction.
In simple words: Complex food is broken into simple molecules.

Teacher's Note:
1. Key idea: Complex food is broken into simple molecules.
2. Write the answer in one clear line.

Question 9. Which of the following represents an exothermic reaction? (i) CaCO₃ →^heat CaO + CO₂ (ii) C + O₂ → CO₂ + Heat
Answer:
(ii) is exothermic because heat is released. Reaction (i) needs heat, so it is endothermic.
In simple words: Heat on the product side means exothermic.

Teacher's Note:
1. Key idea: Heat on the product side means exothermic.
2. Write the answer in one clear line.

Question 10. Name the type of reaction involved in the following: CuSO₄ + Zn → ZnSO₄ + Cu
Answer:
A displacement reaction: zinc displaces copper from copper sulphate.
In simple words: The more reactive zinc replaces copper.

Teacher's Note:
1. Key idea: The more reactive zinc replaces copper.
2. Write the answer in one clear line.

Question 11. What is the reaction called in which one substance is oxidised and the other is reduced?
Answer:
A redox reaction.
In simple words: Oxidation and reduction together.

Teacher's Note:
1. Key idea: Oxidation and reduction together.
2. Write the answer in one clear line.

Question 12. Name the reaction in which oxygen is added to a substance.
Answer:
Oxidation.
In simple words: Gain of oxygen is oxidation.

Teacher's Note:
1. Key idea: Gain of oxygen is oxidation.
2. Write the answer in one clear line.

Question 13. Name two effects of oxidation in daily life.
Answer:
(i) Corrosion (rusting)
(ii) Rancidity
In simple words: Metals rust and fatty food turns rancid.

Teacher's Note:
1. Key idea: Metals rust and fatty food turns rancid.
2. Write the answer in one clear line.

Question 14. Why do iron articles become brown after some time?
Answer:
Iron is slowly corroded by moist air to form a brown coating of rust (hydrated iron(III) oxide).
In simple words: Rusting needs air and moisture.

Teacher's Note:
1. Key idea: Rusting needs air and moisture.
2. Write the answer in one clear line.

Question 15. Why do the colour and taste of fats and oils change after sometimes?
Answer:
Because of rancidity: oxidation of the fats and oils by air.
In simple words: Air spoils oils and fats.

Teacher's Note:
1. Key idea: Air spoils oils and fats.
2. Write the answer in one clear line.

Question 16. Write two conditions of corrosion.
Answer:
(i) Presence of moisture (water). (ii) Presence of air (oxygen).
In simple words: Both air and water are needed.

Teacher's Note:
1. Key idea: Both air and water are needed.
2. Write the answer in one clear line.

Question 17. Complete the missing component/variable given as X and Y in the following reaction: Zn(s) + H₂SO₄(aq) → ZnSO₄(X) + H₂(Y)
Answer:
X = (aq), because zinc sulphate dissolves in water. Y = (g), because hydrogen is a gas.
In simple words: (aq) is a solution, (g) is a gas.

Teacher's Note:
1. Key idea: (aq) is a solution, (g) is a gas.
2. Write the answer in one clear line.

Question 18. Give the chemical name of the reactants as well as the products of the following chemical equation: HNO₃ + Ca(OH)₂ → Ca(NO₃)₂ + H₂O
Answer:
Reactants: nitric acid (HNO₃) and calcium hydroxide (Ca(OH)₂). Products: calcium nitrate (Ca(NO₃)₂) and water. Balanced: 2HNO₃ + Ca(OH)₂ → Ca(NO₃)₂ + 2H₂O
In simple words: The equation also needs the coefficient 2 before HNO₃ and H₂O.

Teacher's Note:
1. Key idea: The equation also needs the coefficient 2 before HNO₃ and H₂O.
2. Write the answer in one clear line.