Mole Concept — Set 2
Chemistry · मोल संकल्पना · Questions 11–20 of 40
How many moles of solute are present in 250 mL of a 2.0 M solution?
Correct Answer: C. 0.50 mol
Option C is correct because moles = M × V(L) = 2.0 × 0.250 = 0.50 mol. Volume must be in liters for molarity calculations. This gives the amount of solute dissolved.
The dilution equation for solutions is?
Correct Answer: B. M1V1 = M2V2
Option B is correct because during dilution, moles of solute remain constant so M1V1 = M2V2. Only solvent is added and solute amount does not change. This relation helps find new concentration or volume.
Mass percent (% by mass) of a solute in a solution is?
Correct Answer: C. (mass of solute/mass of solution) × 100
Option C is correct because mass percent equals mass of solute divided by mass of solution times 100. The mass of solution includes both solute and solvent. It is useful when masses are known directly.
Molality (m) of a solution is defined as?
Correct Answer: C. Moles of solute per kilogram of solvent
Option C is correct because molality is moles of solute per kg of solvent. It depends on mass, not volume. Therefore, it is less affected by temperature changes.
Mole fraction of a component in a mixture is?
Correct Answer: A. Moles of component/total moles of all components
Option A is correct because mole fraction is moles of a component divided by total moles. It has no unit because it is a ratio. The sum of all mole fractions in a mixture is 1.
In a chemical reaction, the limiting reagent is the reactant that?
Correct Answer: C. Gets completely consumed first and limits product formation
Option C is correct because the limiting reagent is used up first and controls the maximum product. Other reactants remain in excess after reaction. Identifying it requires comparing required mole ratios.
For the reaction 2H2 + O2 → 2H2O, if 5 mol H2 reacts with 2 mol O2, which statement is correct?
Correct Answer: D. O2 is limiting and 4 mol H2O can form
Option D is correct because 5 mol H2 would need 2.5 mol O2 but only 2 mol O2 is available. So O2 is limiting and water formed = 2 × 2 = 4 mol. Extra H2 remains unreacted after completion.
What is the mass of 0.20 mol of NaCl? (Na=23, Cl=35.5)?
Correct Answer: D. 11.7 g
Option D is correct because molar mass of NaCl = 23 + 35.5 = 58.5 g/mol. Mass = moles × molar mass = 0.20 × 58.5 = 11.7 g. This converts amount in moles to mass in grams.
In dilute aqueous solutions, 5 ppm of a solute is approximately equal to?
Correct Answer: B. 5 mg/L
Option B is correct because in water, 1 ppm is roughly 1 mg/L for very dilute solutions. So 5 ppm is about 5 mg/L. This approximation uses water density near 1 g/mL.
How many atoms are present in 0.10 mol of sodium (Na)?
Correct Answer: A. 6.022 × 10^22 atoms
Option A is correct because atoms = moles × NA = 0.10 × 6.022 × 10^23. This equals 6.022 × 10^22 atoms. The mole directly converts between moles and particles.