Mole Concept — Set 4
Chemistry · मोल संकल्पना · Questions 31–40 of 40
What is the molarity of a solution containing 5.85 g NaCl in 1.0 L of solution? (NaCl = 58.5 g/mol)?
Correct Answer: B. 0.10 M
• **0.10 M** = Option B is correct because moles of NaCl = 5. • **mass** — This uses molar mass to convert grams into moles • 💡 Wrong-option analysis: A: 0.01 M; C: 10 M; D: 1.0 M
How much 10.0 M stock solution is needed to prepare 250 mL of 1.0 M solution?
Correct Answer: B. 25 mL
• **25 mL** = Option B is correct because M1V1 = M2V2 gives V1 = (1. • **1** — Option B is correct because M1V1 = M2V2 gives V1 = (1 • 💡 Wrong-option analysis: A: 250 mL; C: 5 mL; D: 2.5 mL
At STP, what volume is occupied by 0.75 mol of an ideal gas?
Correct Answer: D. 16.8 L
• **16.8 L** = Option D is correct because V = n × 22. • (Contextual detail from explanation) • 💡 Wrong-option analysis: A: 22.4 L; B: 12.6 L; C: 7.5 L
How many molecules are present in 18 g of water (H2O)?
Correct Answer: B. 6.022 × 10^23
• **6.022 × 10^23** = Option B is correct because 18 g of water is 1 mole of H2O. • **18** — Option B is correct because 18 g of water is 1 mole of H2O • 💡 Wrong-option analysis: A: 3.011 × 10^23; C: 1.2044 × 10^24; D: 6.022 × 10^22
For acid-base reactions, 1.0 M H2SO4 solution is approximately equal to?
Correct Answer: A. 2.0 N
• **2.0 N** = Option A is correct because H2SO4 can provide 2 H+ ions, so n-factor is 2. • **4** — Option A is correct because H2SO4 can provide 2 H+ ions, so n-factor is 2 • 💡 Wrong-option analysis: B: 1.5 N; C: 0.5 N; D: 1.0 N
How many moles are present in 3.011 × 10^23 molecules of a substance?
Correct Answer: C. 0.50 mol
• **0.50 mol** = Option C is correct because moles = number of molecules/NA = 3. • (Contextual detail from explanation) • 💡 Wrong-option analysis: A: 2.00 mol; B: 1.00 mol; D: 0.25 mol
What is the mass of 0.20 mol of aluminium atoms? (Al = 27 g/mol)?
Correct Answer: A. 5.4 g
• **5.4 g** = Option A is correct because mass = moles × molar mass = 0. • **mass** — Option A is correct because mass = moles × molar mass = 0 • 💡 Wrong-option analysis: B: 54 g; C: 2.7 g; D: 27 g
For N2 + 3H2 → 2NH3, if 1 mol N2 reacts with 2 mol H2, the maximum NH3 formed is?
Correct Answer: B. 1.33 mol
• **1.33 mol** = Option B is correct because 2 mol H2 is limiting since 3 mol H2 is needed for 1 mol N2. • **3** — Option B is correct because 2 mol H2 is limiting since 3 mol H2 is needed for... • 💡 Wrong-option analysis: A: 2.0 mol; C: 1.0 mol; D: 0.67 mol
The density of a gas at STP is 2.0 g/L. Its molar mass is approximately?
Correct Answer: B. 44.8 g/mol
• **44.8 g/mol** = Option B is correct because molar mass ≈ density × molar volume at STP = 2. • **mass** — Option B is correct because molar mass ≈ density × molar volume at STP = 2 • 💡 Wrong-option analysis: A: 4.0 g/mol; C: 2.0 g/mol; D: 22.4 g/mol
An impure CaCO3 sample of mass 10 g releases 2.2 g CO2 on heating (CaCO3 → CaO + CO2). The percentage purity of CaCO3 is?
Correct Answer: D. 50%
• **50%** = Option D is correct because moles CO2 = 2. • **5** — 05 mol, so moles CaCO3 = 0 • 💡 Wrong-option analysis: A: 75%; B: 25%; C: 90%