Questions About Molality
Multiple-Choice Questions – Molality
1. What does molality (m) represent?
A) Moles of solute per liter of solvent
B) Moles of solute per kilogram of solvent
C) Moles of solute per gram of solute
D) Grams of solute per kilogram of solvent
E) Moles of solute per milliliter of solution
2. What is the unit of molality?
A) mol/L
B) g/kg
C) mol/kg
D) mol/mL
E) mol/g
3. If 2 moles of NaCl are dissolved in 1 kg of water, what is the molality?
A) 0.5 m
B) 1 m
C) 2 m
D) 3 m
E) 4 m
4. A solution contains 0.5 mol of solute in 0.25 kg of solvent. What is the molality?
A) 0.25 m
B) 0.5 m
C) 1.0 m
D) 2.0 m
E) 4.0 m
5. Which of the following factors does not affect molality?
A) Amount of solute
B) Mass of solvent
C) Volume of solvent
D) Temperature
E) Volume of solution
6. What is the molality if 0.1 mol of solute is dissolved in 200 g of solvent?
A) 0.2 m
B) 0.5 m
C) 1.0 m
D) 2.0 m
E) 5.0 m
7. Which is required to calculate molality?
A) Moles of solute and volume of solution
B) Moles of solute and temperature
C) Moles of solute and mass of solvent
D) Mass of solute and volume of solvent
E) Volume of solution and temperature
8. What is the molality of a solution with 10 g NaOH (molar mass = 40 g/mol) in 500 g of water?
A) 0.25 m
B) 0.5 m
C) 1.0 m
D) 2.0 m
E) 4.0 m
9. What is the molality of a solution with 36 g of glucose (molar mass = 180 g/mol) in 0.2 kg of water?
A) 0.2 m
B) 0.5 m
C) 1.0 m
D) 2.0 m
E) 3.0 m
10. Molality is preferred over molarity when:
A) The solution is very dilute
B) Temperature varies
C) Working with gases
D) Solvent evaporates easily
E) Dealing with pure liquids
11. Which expression correctly defines molality (m)?
A) mol solute / L solution
B) g solute / kg solvent
C) mol solute / kg solvent
D) mol solute / g solvent
E) mol solute × kg solvent
12. What is the molality of a solution prepared with 0.2 mol of solute and 400 g of solvent?
A) 0.2 m
B) 0.4 m
C) 0.5 m
D) 0.8 m
E) 1.0 m
13. A solution contains 5 moles of solute in 2 kg of water. What is its molality?
A) 2.5 m
B) 1.0 m
C) 3.0 m
D) 5.0 m
E) 10.0 m
14. What is the molality of 18 g of H₂O₂ (molar mass = 34 g/mol) dissolved in 0.5 kg of solvent?
A) 0.5 m
B) 1.0 m
C) 1.2 m
D) 2.0 m
E) 2.5 m
15. What mass of solvent (in kg) is needed to prepare a 1 m solution using 2 moles of solute?
A) 0.25
B) 0.5
C) 1
D) 2
E) 3
16. If 0.4 mol of solute is added to 0.2 kg of water, the molality is:
A) 1.0 m
B) 2.0 m
C) 3.0 m
D) 4.0 m
E) 5.0 m
17. Which one of the following is a concentrated solution in terms of molality?
A) 0.01 m
B) 0.1 m
C) 1 m
D) 3 m
E) 0.5 m
18. What is the molality if 1 mole of solute is added to 250 g of solvent?
A) 0.25 m
B) 1.0 m
C) 2.0 m
D) 3.0 m
E) 4.0 m
19. A solution has 0.6 mol of solute and 300 g of solvent. The molality is:
A) 0.5 m
B) 1.0 m
C) 1.5 m
D) 2.0 m
E) 2.5 m
20. In molality calculations, the mass of solvent must be expressed in:
A) Milliliters
B) Kilograms
C) Grams
D) Moles
E) Liters
- Questions on Saturated and Unsaturated Solutions
- Questions on Solubility and Henry's Law of Solubility
- Questions About Molarity
Answer Key with Full Explanations
1. B – Molality = moles of solute per kilogram of solvent.
2. C – Unit of molality is mol/kg.
3. C – 2 mol / 1 kg = 2 m.
4. D – 0.5 mol / 0.25 kg = 2.0 m.
5. C – Volume is irrelevant to molality.
6. D – 0.1 mol / 0.2 kg = 0.5 m.
7. C – You need moles of solute and mass of solvent (in kg).
8. A – 10 g / 40 = 0.25 mol; 0.25 / 0.5 kg = 0.5 m.
9. B – 36 g / 180 = 0.2 mol; 0.2 / 0.2 kg = 1.0 m.
10. B – Molality is independent of temperature since it’s mass-based.
11. C – Molality = mol solute / kg solvent.
12. C – 0.2 mol / 0.4 kg = 0.5 m.
13. A – 5 mol / 2 kg = 2.5 m.
14. B – 18 / 34 = 0.53 mol ≈ 1.0 m.
15. D – 2 mol / x kg = 1 m → x = 2 kg.
16. B – 0.4 / 0.2 = 2.0 m.
17. D – 3 mol/kg is a high concentration = concentrated.
18. C – 1 mol / 0.25 kg = 4.0 m.
19. C – 0.6 / 0.3 = 2.0 m.
20. B – Solvent must be in kilograms for correct molality.
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