“Stoichiometry” MCQ with Answer Explanation.

71. How many moles of NH₄Cl are present in 58.5 g? (Molar mass of NH₄Cl = 53.5 g/mol)

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

Answer: A) 1 mole

Explanation: Moles = mass / molar mass = 58.5 g / 53.5 g/mol = 1.09 moles.

72. What is the mass of 2 moles of sodium bicarbonate (NaHCO₃)? (Molar mass of NaHCO₃ = 84 g/mol)

A) 168 g
B) 120 g
C) 96 g
D) 80 g

Answer: A) 168 g

Explanation: Mass = moles × molar mass = 2 moles × 84 g/mol = 168 g.

73. How many moles of H₂O can be produced from the complete combustion of 3 moles of C₃H₈? (C₃H₈ + 5O₂ → 3CO₂ + 4H₂O)

A) 6 moles
B) 8 moles
C) 12 moles
D) 15 moles

Answer: B) 12 moles

Explanation: The reaction shows that 1 mole of C₃H₈ produces 4 moles of H₂O, so 3 moles of C₃H₈ will produce 3 × 4 = 12 moles of H₂O.

74. If you have 10 g of CaCO₃, how many moles do you have? (Molar mass of CaCO₃ = 100 g/mol)

A) 0.1 moles
B) 0.5 moles
C) 1 mole
D) 2 moles

Answer: C) 0.1 moles

Explanation: Moles = mass / molar mass = 10 g / 100 g/mol = 0.1 moles.

75. In the reaction 2Na + Cl₂ → 2NaCl, what is the mass of sodium chloride produced from 3 moles of Na? (Molar mass of NaCl = 58.5 g/mol)

A) 87.75 g
B) 174 g
C) 117 g
D) 75 g

Answer: B) 174 g

Explanation: 3 moles of Na produce 3 moles of NaCl, so mass = 3 × 58.5 g/mol = 175.5 g.

76. What is the total number of moles in a solution containing 2 moles of NaCl and 3 moles of KCl?

A) 2 moles
B) 3 moles
C) 5 moles
D) 6 moles

Answer: D) 5 moles

Explanation: The total number of moles = 2 moles (NaCl) + 3 moles (KCl) = 5 moles.

77. How many liters of oxygen gas are needed to completely react with 4 moles of propane (C₃H₈)? (C₃H₈ + 5O₂ → 3CO₂ + 4H₂O)

A) 44.8 L
B) 56.8 L
C) 67.2 L
D) 88.4 L

Answer: D) 88.4 L

Explanation: 1 mole of C₃H₈ reacts with 5 moles of O₂, so 4 moles of C₃H₈ will require 4 × 5 = 20 moles of O₂. At STP, volume = 20 × 22.4 L = 448 L.

78. How many grams of Fe₂O₃ are produced from 4 moles of Fe? (4Fe + 3O₂ → 2Fe₂O₃; Molar mass of Fe₂O₃ = 160 g/mol)

A) 80 g
B) 160 g
C) 240 g
D) 320 g

Answer: C) 240 g

Explanation: 4 moles of Fe will produce 2 moles of Fe₂O₃. Thus, mass = 2 × 160 g/mol = 320 g.

79. If you have 100 g of glucose (C₆H₁₂O₆), how many moles do you have? (Molar mass of glucose = 180 g/mol)

A) 0.5 moles
B) 1 mole
C) 2 moles
D) 3 moles

Answer: A) 0.55 moles

Explanation: Moles = mass / molar mass = 100 g / 180 g/mol = 0.56 moles.

80. In the reaction 2H₂ + O₂ → 2H₂O, how many grams of water are produced from 4 moles of H₂? (Molar mass of H₂O = 18 g/mol)

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

Answer: A) 72 g

Explanation: 4 moles of H₂ produce 4 moles of H₂O, so mass = 4 × 18 g/mol = 72 g.