“Stoichiometry” MCQ with Answer Explanation.

91. In the reaction 2Na + 2H₂O → 2NaOH + H₂, how many moles of hydrogen gas are produced from 3 moles of Na?

A) 1.5 moles
B) 2 moles
C) 3 moles
D) 4.5 moles

Answer: A) 1.5 moles

Explanation: The balanced equation shows that 2 moles of Na produce 1 mole of H₂, so 3 moles of Na produce (3/2) moles of H₂ = 1.5 moles.

92. How many grams of H₂O are produced from the combustion of 1 mole of methane (CH₄)? (CH₄ + 2O₂ → CO₂ + 2H₂O; Molar mass of H₂O = 18 g/mol)

A) 18 g
B) 36 g
C) 54 g
D) 72 g

Answer: A) 36 g

Explanation: 1 mole of CH₄ produces 2 moles of H₂O, so mass = 2 × 18 g/mol = 36 g.

93. How many moles of H₂ are in 22 g of H₂ gas? (Molar mass of H₂ = 2 g/mol)

A) 5 moles
B) 10 moles
C) 15 moles
D) 20 moles

Answer: B) 11 moles

Explanation: Moles = mass / molar mass = 22 g / 2 g/mol = 11 moles.

94. What is the molar mass of ammonium phosphate ((NH₄)₃PO₄)?

A) 132 g/mol
B) 149 g/mol
C) 194 g/mol
D) 250 g/mol

Answer: C) 149 g/mol

Explanation: Molar mass = (3×14) + (12×1) + (31) + (4×16) = 42 + 12 + 31 + 64 = 149 g/mol.

95. If you have 50 g of NaCl, how many moles do you have? (Molar mass of NaCl = 58.5 g/mol)

A) 0.85 moles
B) 1 mole
C) 1.5 moles
D) 2 moles

Answer: A) 0.85 moles

Explanation: Moles = mass / molar mass = 50 g / 58.5 g/mol ≈ 0.85 moles.

96. In the reaction 2C₂H₆ + 7O₂ → 4CO₂ + 6H₂O, how many moles of water are produced from 3 moles of C₂H₆?

A) 6 moles
B) 9 moles
C) 12 moles
D) 18 moles

Answer: B) 9 moles

Explanation: The reaction indicates that 2 moles of C₂H₆ produce 6 moles of H₂O, so 3 moles of C₂H₆ will produce (3/2) × 6 = 9 moles.

97. How many grams of glucose are in 0.5 moles? (Molar mass of glucose = 180 g/mol)

A) 45 g
B) 90 g
C) 180 g
D) 360 g

Answer: B) 90 g

Explanation: Mass = moles × molar mass = 0.5 moles × 180 g/mol = 90 g.

98. In the reaction 3Fe + 2O₂ → Fe₃O₄, how many moles of Fe₃O₄ can be produced from 6 moles of Fe?

A) 2 moles
B) 3 moles
C) 4 moles
D) 5 moles

Answer: A) 2 moles

Explanation: The balanced equation shows that 3 moles of Fe produce 1 mole of Fe₃O₄, so 6 moles of Fe will produce 2 moles of Fe₃O₄.

99. How many liters of carbon dioxide gas are produced when 2 moles of glucose are completely oxidized? (C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O; at STP 1 mole = 22.4 L)

A) 22.4 L
B) 44.8 L
C) 134.4 L
D) 268.8 L

Answer: C) 134.4 L

Explanation: 2 moles of glucose produce 12 moles of CO₂. Thus, volume = 12 moles × 22.4 L/mole = 268.8 L.

100. How many moles of NaOH can be formed from the reaction of 2 moles of Na with 2 moles of water? (2Na + 2H₂O → 2NaOH + H₂)

A) 1 mole
B) 2 moles
C) 3 moles
D) 4 moles

Answer: B) 2 moles

Explanation: The balanced equation shows that 2 moles of Na react to produce 2 moles of NaOH.