Stoichiometric Relationships Practice Questions
IB (International Baccalaureate) · IB Chemistry HL · 137 free MCQs with instant results and detailed explanations.
137
Total
35
Easy
80
Medium
22
Hard
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Sample Questions from Stoichiometric Relationships
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Q1
Easy
In the reaction 2H2 + O2 → 2H2O, how many moles of water are produced from 3 moles of O2?
A.
3 moles
B.
4 moles
C.
6 moles
D.
1.5 moles
Show Answer & Explanation
Correct Answer: C
According to the balanced equation, 1 mole of O2 produces 2 moles of H2O. Therefore, 3 moles of O2 will produce 3 x 2 = 6 moles of H2O.
Q2
Easy
In a chemical reaction, if 3 moles of hydrogen react with 1 mole of nitrogen, how many moles of ammonia (NH₃) are produced?
A.
3 moles
B.
2 moles
C.
6 moles
D.
1 mole
Show Answer & Explanation
Correct Answer: A
The balanced equation for the formation of ammonia is N₂ + 3H₂ → 2NH₃. Thus, 3 moles of H₂ yield 2 moles of NH₃, meaning 1.5 moles of NH₃ are produced per mole of N₂ reacted. If 3 moles of H₂ react, 3 moles of NH₃ are produced.
Q3
Easy
If 5 g of sodium chloride (NaCl) is dissolved in 250 mL of water, what is the concentration in mol/L (M)? (Molar mass of NaCl = 58.5 g/mol)
A.
0.34 M
B.
0.25 M
C.
0.50 M
D.
0.15 M
Show Answer & Explanation
Correct Answer: A
Concentration (M) is calculated using the formula: M = moles of solute/volume of solution (L). First, calculate moles of NaCl: 5 g / 58.5 g/mol = 0.0855 moles. Then convert 250 mL to L: 250 mL = 0.250 L. Therefore, concentration = 0.0855 moles / 0.250 L = 0.34 M.
Q4
Medium
What is the molar mass of glucose (C6H12O6)?
A.
180 g/mol
B.
162 g/mol
C.
150 g/mol
D.
198 g/mol
Show Answer & Explanation
Correct Answer: A
The molar mass of glucose is calculated as follows: C (12 g/mol) * 6 + H (1 g/mol) * 12 + O (16 g/mol) * 6 = 180 g/mol, confirming A is correct.
Q5
Medium
In a reaction where 4 moles of A react with 3 moles of B to produce 5 moles of C, what is the limiting reagent if only 3 moles of A and 2 moles of B are available?
A.
A
B.
B
C.
C
D.
Neither
Show Answer & Explanation
Correct Answer: B
To find the limiting reagent, we compare the mole ratio required: 4:3. Available moles of A (3) would need 2.25 moles of B, but only 2 moles are present, making B the limiting reagent.
Q6
Medium
Which of the following statements about stoichiometric coefficients in a balanced equation is true?
A.
They represent the actual masses of the reactants and products.
B.
They indicate the number of moles of each substance involved in the reaction.
C.
They can vary depending on the temperature of the reaction.
D.
They are always whole numbers, reflecting the number of atoms in a molecule.
Show Answer & Explanation
Correct Answer: B
Stoichiometric coefficients in a balanced equation represent the ratio of moles of reactants and products involved in a chemical reaction, which is crucial for calculations in stoichiometry.
Q7
Medium
If 50 g of ethyl alcohol (C₂H₅OH) is combusted completely, how many grams of carbon dioxide (CO₂) are produced?
A.
88 g
B.
44 g
C.
132 g
D.
22 g
Show Answer & Explanation
Correct Answer: A
The balanced combustion reaction for ethyl alcohol is C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O. The molar mass of C₂H₅OH is 46 g/mol. 50 g corresponds to approximately 1.087 moles, producing 2.174 moles of CO₂. The mass of CO₂ is 2.174 moles × 44 g/mol = 88 g.
Q8
Hard
A sample of ethane (C2H6) is combusted in excess oxygen. If 0.5 moles of ethane are burned, how many moles of carbon dioxide (CO2) are produced in the reaction?
A.
0.5 moles
B.
1.0 moles
C.
1.5 moles
D.
2.0 moles
Show Answer & Explanation
Correct Answer: B
The balanced equation for the combustion of ethane is C2H6 + 7/2 O2 → 2 CO2 + 3 H2O. From this, we see that burning 1 mole of ethane produces 2 moles of CO2. Therefore, 0.5 moles of ethane will produce 0.5 * 2 = 1.0 moles of CO2.
Q9
Hard
In a reaction where 3 moles of A react with 2 moles of B to produce 4 moles of C, if 9 moles of A are available, how many moles of B are required to completely react with A?
A.
6 moles
B.
4 moles
C.
3 moles
D.
8 moles
Show Answer & Explanation
Correct Answer: A
The mole ratio from the balanced reaction is 3 moles of A to 2 moles of B. If 9 moles of A are used, the amount of B required can be calculated using the ratio: (9 moles A) * (2 moles B / 3 moles A) = 6 moles of B.
Q10
Hard
In a reaction between 2 moles of hydrogen gas and 1 mole of oxygen gas to produce water, how many grams of water can be produced if 4 moles of hydrogen are reacted?
A.
72 g
B.
36 g
C.
18 g
D.
144 g
Show Answer & Explanation
Correct Answer: A
From 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. The molar mass of water (H₂O) is 18 g/mol, so 4 moles of water is 4 * 18 g = 72 g.
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Stoichiometric Relationships — IB (International Baccalaureate) IB Chemistry HL Practice Questions Online
This page contains 137 practice MCQs for the chapter Stoichiometric Relationships in IB (International Baccalaureate) IB Chemistry HL. The questions are organized by difficulty — 35 easy, 80 medium, 22 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.