Mole Concept — Set 3
Chemistry · मोल संकल्पना · Questions 21–30 of 40
The charge carried by 1 mole of electrons is approximately?
Correct Answer: D. 9.65 × 10^4 C
• **9.65 × 10^4 C** = Option D is correct because 1 mole of electrons carries about 9. • **4** — 65 × 10^4 C of charge • 💡 Wrong-option analysis: A: 1.602 × 10^-19 C; B: 9.8 C; C: 3.00 × 10^8 C
Gram molecular mass of a substance means?
Correct Answer: C. Mass of 1 mole expressed in grams
• **Mass of 1 mole expressed in grams** = Option C is correct because gram molecular mass is the mass of one mole in grams. • **mass** — Option C is correct because gram molecular mass is the mass of one mole in grams • 💡 Wrong-option analysis: A: Mass of 1 atom expressed in grams; B: Mass of 1 molecule expressed in grams; D: Mass of 1 liter of gas at STP
At STP, the volume occupied by 0.50 mol of an ideal gas is?
Correct Answer: C. 11.2 L
• **11.2 L** = Option C is correct because volume at STP = moles × 22. • (Contextual detail from explanation) • 💡 Wrong-option analysis: A: 22.4 L; B: 5.6 L; D: 44.8 L
Why does molarity generally change with temperature?
Correct Answer: C. Because solution volume can change with temperature
• **Because solution volume can change with temperature** = Option C is correct because molarity depends on volume of solution, which can expand or contract with temperature. • (Contextual detail from explanation) • 💡 Wrong-option analysis: A: Because molar mass changes; B: Because Avogadro number changes; D: Because number of moles of solute changes
Why is molality generally considered temperature independent?
Correct Answer: A. Because it uses mass of solvent, not volume
• **Because it uses mass of solvent, not volume** = Option A is correct because molality is based on mass of solvent, which does not change with temperature. • **mass** — Option A is correct because molality is based on mass of solvent, which does ... • 💡 Wrong-option analysis: B: Because it uses pressure of gas; C: Because it uses volume of solvent; D: Because it uses volume of solution
For any mixture, the sum of mole fractions of all components is?
Correct Answer: D. Equal to 1
• **Equal to 1** = The correct answer is 'Equal to 1'. • (Contextual detail from explanation) • 💡 Wrong-option analysis: A: Always greater than 1; B: Always less than 1; C: Equal to 0
How much NaOH is needed to prepare 500 mL of 0.20 M NaOH solution? (NaOH = 40 g/mol)?
Correct Answer: C. 4.0 g
• **4.0 g** = Option C is correct because moles needed = M × V(L) = 0. • **Mass** — Mass = moles × molar mass = 0 • 💡 Wrong-option analysis: A: 0.4 g; B: 40 g; D: 2.0 g
How many formula units are present in 2.5 g of CaCO3? (CaCO3 = 100 g/mol)?
Correct Answer: A. 1.5055 × 10^22
• **1.5055 × 10^22** = Option A is correct because moles = 2. • **3** — 022 × 10^23 = 1 • 💡 Wrong-option analysis: B: 3.011 × 10^22; C: 6.022 × 10^22; D: 1.5055 × 10^23
A compound contains 40.0% C, 6.67% H, and 53.33% O by mass. Its empirical formula is?
Correct Answer: C. CH2O
• **CH2O** = Option C is correct because moles in 100 g are C:40/12=3. • **100** — Option C is correct because moles in 100 g are C:40/12=3 • 💡 Wrong-option analysis: A: CH4O; B: C3H6O3; D: C2H4O2
If the empirical formula is CH2O and the molar mass is 180 g/mol, the molecular formula is?
Correct Answer: A. C6H12O6
• **C6H12O6** = Option A is correct because empirical mass of CH2O is 12+2+16 = 30 g/mol. • **30** — Option A is correct because empirical mass of CH2O is 12+2+16 = 30 g/mol • 💡 Wrong-option analysis: B: C5H10O5; C: C2H4O2; D: C3H6O3