Stoichiometry Practice Questions
IGCSE (Cambridge) · IGCSE Chemistry · 133 free MCQs with instant results and detailed explanations.
133
Total
42
Easy
67
Medium
24
Hard
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Sample Questions from Stoichiometry
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Q1
Easy
What is the mole ratio of hydrogen to oxygen in the reaction for the formation of water (2H₂ + O₂ → 2H₂O)?
A.
1:1
B.
2:1
C.
2:2
D.
1:2
Show Answer & Explanation
Correct Answer: B
The balanced equation shows that 2 moles of hydrogen react with 1 mole of oxygen, giving a mole ratio of 2:1.
Q2
Easy
If 4 moles of sodium react with 1 mole of chlorine gas to produce sodium chloride, how many moles of sodium chloride are produced?
A.
1
B.
2
C.
4
D.
5
Show Answer & Explanation
Correct Answer: C
According to the reaction 4Na + Cl₂ → 4NaCl, 4 moles of sodium yield 4 moles of sodium chloride, thus the answer is 4.
Q3
Easy
In a reaction where 10 grams of calcium carbonate (CaCO₃) decomposes, how many grams of calcium oxide (CaO) will be formed, given that the molar mass of CaCO₃ is 100 g/mol and CaO is 56 g/mol?
A.
28 g
B.
40 g
C.
56 g
D.
34 g
Show Answer & Explanation
Correct Answer: A
The decomposition of CaCO₃ produces CaO and CO₂. From 100 g of CaCO₃, 56 g of CaO is formed. Thus, from 10 g, the calculation gives 28 g.
Q4
Medium
If 2 moles of hydrogen react with 1 mole of oxygen to produce water, how many moles of water can be formed from 4 moles of hydrogen?
A.
2 moles
B.
4 moles
C.
6 moles
D.
8 moles
Show Answer & Explanation
Correct Answer: B
According to the reaction 2H₂ + O₂ → 2H₂O, 2 moles of H₂ produce 2 moles of H₂O. Therefore, 4 moles of H₂ will produce 4 moles of H₂O.
Q5
Medium
In the reaction 2H₂ + O₂ → 2H₂O, if you start with 3 moles of O₂, how many moles of H₂ are needed to react completely?
A.
2 moles
B.
3 moles
C.
4 moles
D.
6 moles
Show Answer & Explanation
Correct Answer: D
The balanced equation indicates a 2:1 ratio of H₂ to O₂. Thus, for 3 moles of O₂, you need 3 x 2 = 6 moles of H₂ for complete reaction.
Q6
Medium
If 5 moles of ammonia (NH₃) are produced from 3 moles of nitrogen (N₂) and 9 moles of hydrogen (H₂), what is the limiting reactant?
A.
Nitrogen
B.
Hydrogen
C.
Ammonia
D.
No limiting reactant
Show Answer & Explanation
Correct Answer: A
The reaction is N₂ + 3H₂ → 2NH₃. To produce 5 moles of NH₃, you would need 7.5 moles of H₂ (3.75 moles N₂). Since only 3 moles of N₂ are available, nitrogen is the limiting reactant.
Q7
Medium
What is the molar mass of sodium bicarbonate (NaHCO₃)?
A.
84 g/mol
B.
100 g/mol
C.
75 g/mol
D.
90 g/mol
Show Answer & Explanation
Correct Answer: A
The molar mass of sodium bicarbonate is calculated as follows: Na (23 g/mol) + H (1 g/mol) + C (12 g/mol) + 3O (16 g/mol) = 23 + 1 + 12 + 48 = 84 g/mol.
Q8
Hard
If 25 g of sodium chloride (NaCl) is dissolved in water to prepare a solution, what is the number of moles of NaCl in that solution? (Molar mass of NaCl = 58.5 g/mol)
A.
0.43 moles
B.
0.75 moles
C.
1.00 moles
D.
1.50 moles
Show Answer & Explanation
Correct Answer: A
To find the number of moles, use the formula: Moles = Mass (g) / Molar mass (g/mol). Here, Moles = 25 g / 58.5 g/mol = 0.427 moles, which rounds to 0.43 moles.
Q9
Hard
In a reaction where 2 moles of hydrogen gas react with 1 mole of oxygen gas to produce water, how many grams of water can be produced from 4 moles of hydrogen gas?
A.
36 g
B.
18 g
C.
72 g
D.
54 g
Show Answer & Explanation
Correct Answer: C
According to the balanced equation 2 H₂ + O₂ → 2 H₂O, 2 moles of H₂ produce 2 moles of H₂O. From 4 moles of H₂, you can produce 4 moles of H₂O. The molar mass of water (H₂O) is 18 g/mol, so 4 moles * 18 g/mol = 72 g.
Q10
Hard
In a stoichiometric calculation, 50 g of CaCO3 is decomposed to produce CaO and CO2 according to the equation: CaCO3 → CaO + CO2. Calculate the volume of CO2 produced at STP (Standard Temperature and Pressure). (Molar mass of CaCO3 = 100 g/mol)
A.
22.4 liters
B.
11.2 liters
C.
44.8 liters
D.
33.6 liters
Show Answer & Explanation
Correct Answer: B
First, calculate the number of moles of CaCO3: 50 g / 100 g/mol = 0.5 moles of CaCO3. According to the balanced equation, 1 mole of CaCO3 produces 1 mole of CO2. Therefore, 0.5 moles of CaCO3 will produce 0.5 moles of CO2. At STP, 1 mole of gas occupies 22.4 liters. Hence, 0.5 moles of CO2 will occupy 0.5 * 22.4 L = 11.2 liters.
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Stoichiometry — IGCSE (Cambridge) IGCSE Chemistry Practice Questions Online
This page contains 133 practice MCQs for the chapter Stoichiometry in IGCSE (Cambridge) IGCSE Chemistry. The questions are organized by difficulty — 42 easy, 67 medium, 24 hard — so you can choose the right level for your preparation.
Every question includes a detailed explanation to help you understand the concept, not just memorize answers. Take a timed quiz to simulate exam conditions, or practice at your own pace with no time limit.