- How many grams are in 3 moles of Na₂CO₃ (Molar mass = 106 g/mol)?
a) 318 g
b) 250 g
c) 300 g
d) 400 g
Answer: a) 318 g
Explanation: 3 moles × 106 g/mol = 318 g.
- In the reaction: 3H₂ + N₂ → 2NH₃, what is the mole ratio of hydrogen to ammonia?
a) 3:2
b) 1:2
c) 2:3
d) 2:1
Answer: a) 3:2
Explanation: The mole ratio shows that 3 moles of hydrogen produce 2 moles of ammonia.
- The number of moles in 100 g of CaCO₃ (Molar mass = 100 g/mol) is:
a) 0.5 moles
b) 1 mole
c) 2 moles
d) 3 moles
Answer: b) 1 mole
Explanation: 100 g ÷ 100 g/mol = 1 mole.
- What is the volume occupied by 5 moles of an ideal gas at STP?
a) 112 L
b) 134 L
c) 100 L
d) 112.5 L
Answer: a) 112 L
Explanation: 5 moles × 22.4 L/mole = 112 L.
- The molar mass of calcium hydroxide (Ca(OH)₂) is:
a) 74 g/mol
b) 78 g/mol
c) 64 g/mol
d) 70 g/mol
Answer: a) 74 g/mol
Explanation: Molar mass = 40.08 + (2 × 1.01) + (2 × 16) = 74.09 g/mol.
- How many moles are in 36 g of NH₃ (Molar mass = 17 g/mol)?
a) 1 mole
b) 2 moles
c) 3 moles
d) 4 moles
Answer: b) 2 moles
Explanation: 36 g ÷ 17 g/mol ≈ 2.12 moles.
- In the reaction 2K + Cl₂ → 2KCl, what is the mole ratio of potassium to potassium chloride?
a) 1:1
b) 2:2
c) 2:1
d) 1:2
Answer: a) 1:1
Explanation: The coefficients indicate a 1:1 mole ratio between potassium and potassium chloride.
- How many grams are in 0.4 moles of HCl (Molar mass = 36.5 g/mol)?
a) 15 g
b) 14.6 g
c) 12 g
d) 18 g
Answer: b) 14.6 g
Explanation: 0.4 moles × 36.5 g/mol = 14.6 g.
- The mass of 5 moles of Na₂S (Molar mass = 78 g/mol) is:
a) 390 g
b) 380 g
c) 400 g
d) 350 g
Answer: a) 390 g
Explanation: 5 moles × 78 g/mol = 390 g.
- How many moles are in 50 g of KBr (Molar mass = 119 g/mol)?
a) 0.42 moles
b) 0.35 moles
c) 0.50 moles
d) 0.75 moles
Answer: a) 0.42 moles
Explanation: 50 g ÷ 119 g/mol ≈ 0.42 moles.
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