MCQ Questions

Question No. 1

The fixed ratio for H₂O is 2:1. What are the fixed ratios of the atoms in the following compounds?

Answer :

(a) PbBr₂

(b) NO₂

(c) Al₂O₃

(d) Li₂O

(e) CH₄

(f) MgCl₂

Question No. 2

Copy and fill in the table. The first row has been done as an example.

Answer :

Question No. 3

Say whether each statement below is correct or incorrect. If it is incorrect, say why.

Answer :

(a) The Law of Conservation of Mass operates 99% of the time.

(b) The mass of the reactants before a reaction and the mass of the products after that reaction will always balance.

(c) When more reactants are involved in the reaction, the Law of Conservation of Mass is less likely to operate.

(d) In an experiment, we treat 10 g of calcium carbonate with 5 g of acid to produce carbon dioxide. Some of the gas escapes into the air. At the end of the reaction, we weigh the product and find 12.3 g is missing. This proves that conservation of mass is invalid.

(e) The Law of Conservation of Mass applies to solids and liquids, but not to gases.

Question No. 4

Redraw the table in your exercise book and complete it.

Answer :

Question No. 5

Give one term or symbol for each of the following statements:

Answer :

(a) A change that involves the transformation of one or more substances into new substances

(b) The symbolic representation of a chemical reaction

(c) The symbol we use to show ‘yield’ or ‘react to form’

(d) The symbol that we use to show that a compound is in the solid state

Question No. 6

Write balanced equations for these reactions:

Answer :

(a) H₂O₂ → H₂O + O₂

(b) SO₂ + O₂ → SO₃

(c) Al + O₂ → Al₂ O₃

(d) KClO₃ → KCl + O₂

(e) H₂S + O₂→ H₂O + SO₂

(f) CH₄ + O₂ → CO₂ + H₂O

(g) MnO₂ + HCl → MnCl₂ + H₂O + Cl₂

(h) Fe + H₂O → Fe₃ O₄ + H₂

Question No. 7

Sodium hydrogen carbonate (NaHCO₃ ) reacts with sulphuric acid (H₂SO₄ ). The
equation for the reaction is:
2NaHCO₃ (aq) + H₂SO₄(aq) → Na₂ SO₄ (aq) + CO₂ (g) + 2H₂ O(l)

Answer :

(a) State the Law of Conservation of Matter.

(b) This reaction is taking place in an open beaker. Is it possible to verify the Law of Conservation of Matter by measuring the mass before and after the reaction? Explain your answer.

(c) Verify the Law of Conservation of Matter by counting the number of atoms before and after the reaction.

Chapter

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