Chapter-4 Formulae and Stoichiometry — Online MCQ Test
CHEMISTRY · Grade 10 · IGCSE cambridge
Practice Chapter-4 Formulae and Stoichiometry with a free chapter-wise online MCQ test.
This chapter covers: Writing formulae and balanced equations the mole concept and calculating reacting masses and yields..
AI-generated questions from basic to board-exam level, with instant results and explanations.
Chapter-4 Formulae and Stoichiometry — Important Questions & Answers
What is the molar mass of calcium carbonate (CaCO₃)? [Ca = 40, C = 12, O = 16]
- A. 68 g/mol
- B. 100 g/mol
- C. 120 g/mol
- D. 128 g/mol
Answer: B. 100 g/mol
Molar mass = 40 + 12 + (16 × 3) = 40 + 12 + 48 = 100 g/mol.
Molar mass = 40 + 12 + (16 × 3) = 40 + 12 + 48 = 100 g/mol.
How many moles are present in 11 g of carbon dioxide (CO₂)? [C = 12, O = 16]
- A. 0.15 mol
- B. 0.25 mol
- C. 0.35 mol
- D. 0.50 mol
Answer: B. 0.25 mol
Molar mass of CO₂ = 44 g/mol. Number of moles = 11/44 = 0.25 mol.
Molar mass of CO₂ = 44 g/mol. Number of moles = 11/44 = 0.25 mol.
In the reaction 2H₂ + O₂ → 2H₂O, how many moles of water are produced from 3 moles of H₂?
- A. 1.0 mol
- B. 1.5 mol
- C. 3.0 mol
- D. 6.0 mol
Answer: C. 3.0 mol
From the equation, 2 mol H₂ produces 2 mol H₂O (1:1 ratio). So 3 mol H₂ produces 3 mol H₂O.
From the equation, 2 mol H₂ produces 2 mol H₂O (1:1 ratio). So 3 mol H₂ produces 3 mol H₂O.
A compound contains 40% carbon, 6.7% hydrogen, and 53.3% oxygen. What is its empirical formula? [C = 12, H = 1, O = 16]
- A. CH₂O
- B. C₂H₄O₂
- C. CH₄O
- D. C₃H₆O₃
Answer: A. CH₂O
Mole ratio: C = 40/12 = 3.33, H = 6.7/1 = 6.7, O = 53.3/16 = 3.33. Simplest ratio = 1:2:1, giving CH₂O.
Mole ratio: C = 40/12 = 3.33, H = 6.7/1 = 6.7, O = 53.3/16 = 3.33. Simplest ratio = 1:2:1, giving CH₂O.
In a limiting reactant problem, 5 g of calcium reacts with 10 g of chlorine to form CaCl₂. Which is the limiting reactant? [Ca = 40, Cl = 35.5]
- A. Calcium, because it has less mass
- B. Chlorine, because it requires more moles
- C. Calcium, because it produces fewer moles of product
- D. Chlorine, because it has a higher atomic mass
Answer: C. Calcium, because it produces fewer moles of product
Ca: 5/40 = 0.125 mol. Cl₂: 10/71 = 0.141 mol. Reaction: Ca + Cl₂ → CaCl₂ requires 1:1 ratio. Calcium produces only 0.125 mol product (limiting), chlorine can produce 0.141 mol.
Ca: 5/40 = 0.125 mol. Cl₂: 10/71 = 0.141 mol. Reaction: Ca + Cl₂ → CaCl₂ requires 1:1 ratio. Calcium produces only 0.125 mol product (limiting), chlorine can produce 0.141 mol.