NEET UG - Concentration expressions: molality molarity mole fraction percentage by volume and mass Question Bank with Options

1. What is the mole fraction of water in a solution containing 9 g of water (molar mass = 18 g/mol) and 18 g of ethanol (molar mass = 46 g/mol)?

A) 0.5

B) 0.625

C) 0.375

D) 0.25

2. If a solution is 10% (w/w) ethanol and its density is 0.98 g/mL, what is its molarity?

A) 1.68 M

B) 1.92 M

C) 1.71 M

D) 2.11 M

3. What is the molality of a 1.0 M aqueous solution of NaCl (density = 1.05 g/mL, molar mass of NaCl = 58.5 g/mol)?

A) 1.0 m

B) 1.07 m

C) 0.93 m

D) 1.1 m

4. Which concentration unit is most convenient for stoichiometric calculations in solution reactions?

A) Molality

B) Mole fraction

C) Molarity

D) Percentage by mass

5. If 1 mole of solute is dissolved in 1 liter of solvent, which concentration expression is it?

A) Molarity

B) Molality

C) Mole fraction

D) None of these

6. What is the mole fraction of solute if the solution is 20% by mass of NaCl (molar mass = 58.5 g/mol) in water?

A) 0.18

B) 0.82

C) 0.20

D) 0.039

7. If 18 g of glucose (molar mass = 180 g/mol) is dissolved in 100 g of water, what is the molality?

A) 0.1 m

B) 1 m

C) 1.8 m

D) 0.18 m

8. Which concentration unit is often used for very low concentrations of dissolved solids in liquids?

A) Molarity

B) Molality

C) Parts per billion (ppb)

D) Percentage by volume

9. If the molarity of a solution is M, and the density is d (in g/mL), and the molar mass of the solvent is M_solvent, what is the molality (m)?

A) m = (1000 * M) / (1000 * d - M * M_solute)

B) m = (1000 * M) / (1000 * d + M * M_solute)

C) m = (1000 * M) / (1000 * d - M * M_solvent)

D) m = (1000 * M) / (1000 * d + M * M_solvent)

10. A solution of 10% (v/v) acetic acid in water means:

A) 10 mL of acetic acid in 90 mL of water

B) 10 mL of acetic acid in 100 mL of water

C) 10 mL of acetic acid in 100 mL of solution

D) 10 g of acetic acid in 100 mL of solution

11. What is the primary difference between molality and molarity in terms of the denominator?

A) Molality uses volume of solution, Molarity uses mass of solvent

B) Molality uses mass of solvent, Molarity uses volume of solution

C) Molality uses mass of solution, Molarity uses volume of solvent

D) Molality uses volume of solvent, Molarity uses mass of solution

12. If 100 mL of a solution contains 5 g of NaOH, what is the concentration in g/L?

A) 5 g/L

B) 50 g/L

C) 10 g/L

D) 0.5 g/L

13. A solution contains 3 moles of solute and 9 moles of solvent. What is the mole fraction of the solvent?

A) 0.75

B) 0.25

C) 0.5

D) 0.33

14. Which concentration expression is most directly related to the partial pressure of a gaseous solute in a liquid solution according to Henry's Law?

A) Molarity

B) Molality

C) Mole fraction

D) Percentage by mass

15. If a solution has a molarity of 0.5 M and a density of 1.05 g/mL, what is its approximate molality?

A) 0.5 m

B) 0.525 m

C) 0.476 m

D) 1.05 m

16. What does 'ppm' stand for in concentration expressions?

A) Parts per million

B) Percentage per million

C) Pounds per million

D) Particles per million

17. If 1 mole of a solute is dissolved in 250 g of solvent, what is the molality of the solution?

A) 0.25 m

B) 4 m

C) 2.5 m

D) 0.5 m

18. Which of the following concentration units is dimensionless?

A) Molarity

B) Molality

C) Mole fraction

D) Percentage by volume

19. If a solution is prepared by mixing 20 mL of ethanol with 80 mL of water, what is the percentage by volume of ethanol?

A) 20%

B) 25%

C) 16%

D) 80%

20. What is the relationship between molarity (M), density (d), and mass percentage (w/w) of a solution?

A) M = (1000 * M * d) / (100 + M)

B) M = (1000 * w/w * d) / (Molar Mass + w/w)

C) M = (1000 * d * w/w) / (100 * Molar Mass + w/w)

D) M = (1000 * d * w/w) / Molar Mass

21. When is percentage by mass (w/w) most commonly used?

A) For gaseous solutions

B) For liquid solutions where volume changes significantly with temperature

C) For solid solutions and concentrated liquid solutions

D) When the solute is a gas

22. If 1 mole of NaCl (molar mass = 58.44 g/mol) is dissolved in 100 g of water, what is the molality?

A) 0.1 m

B) 1 m

C) 10 m

D) 58.44 m

23. What is the primary advantage of using molality over molarity?

A) It is easier to measure the volume of the solution

B) It is independent of temperature

C) It is directly proportional to the moles of solute

D) It is always a larger number than molarity

24. Consider a solution of ethanol in water. If the percentage by volume is 50%, it means:

A) 50 mL of ethanol in 50 mL of water

B) 50 mL of ethanol in 100 mL of solution

C) 50 g of ethanol in 100 g of solution

D) 50 mL of ethanol in 100 g of solution

25. If the molar mass of a solute is M and its molality is m, what is the mass of the solute in 1 kg of solvent?

A) m * M

B) m / M

C) M / m

D) m

26. Which concentration expression is directly proportional to the mole fraction of the solute?

A) Molarity

B) Molality

C) Percentage by mass

D) None of the above

27. If a solution is 10% (w/v) glucose, it means:

A) 10 g of glucose in 100 g of solution

B) 10 g of glucose in 100 mL of solution

C) 10 mL of glucose in 100 mL of solution

D) 10 g of glucose in 100 g of solvent

28. What is percentage by volume (v/v) defined as?

A) (Volume of solute / Volume of solvent) * 100

B) (Volume of solute / Volume of solution) * 100

C) (Volume of solvent / Volume of solution) * 100

D) (Volume of solution / Volume of solute) * 100

29. Which concentration unit is most appropriate for expressing the concentration of a very dilute solution of a pollutant in water?

A) Molarity

B) Molality

C) Parts per million (ppm)

D) Mole fraction

30. If 1 mole of solute is dissolved in 500 mL of solution, what is the molarity?

A) 0.5 M

B) 1 M

C) 2 M

D) 0.2 M

31. What is the mole fraction of the solvent if the mole fraction of the solute is 0.2?

A) 0.2

B) 0.8

C) 1.0

D) 0.0

32. A solution is prepared by dissolving 5 g of NaCl in 45 g of water. What is the mass percentage of NaCl?

A) 5%

B) 10%

C) 11.1%

D) 90%

33. Which concentration expression is most useful for expressing the concentration of gases dissolved in liquids?

A) Molality

B) Molarity

C) Mole fraction

D) Percentage by volume

34. If 22.4 L of a gas at STP is dissolved in 1 L of solvent, the molarity is approximately:

A) 1 M

B) 0.5 M

C) 2 M

D) 0.1 M

35. What is the unit of molarity?

A) mol/kg

B) mol/L

C) kg/mol

D) L/mol

36. What is the unit of molality?

A) mol/L

B) mol/kg

C) L/mol

D) kg/mol

37. If 10 g of NaOH is dissolved in 90 g of water, what is the mass percentage of NaOH?

A) 10%

B) 90%

C) 11.1%

D) 9.09%

38. Percentage by volume is used when:

A) Both solute and solvent are solids

B) Solute is solid and solvent is liquid

C) Both solute and solvent are liquids

D) Solute is liquid and solvent is solid

39. What is the relationship between molarity (M) and molality (m) for a dilute aqueous solution?

A) M > m

B) M < m

C) M = m

D) No fixed relationship

40. For a dilute solution, which concentration expression is most suitable for expressing the amount of solute?

A) Molarity

B) Molality

C) Mole fraction

D) Parts per million (ppm)

41. Percentage by mass of a component in a solution is defined as:

A) (Mass of solute / Mass of solution) * 100

B) (Mass of solute / Mass of solvent) * 100

C) (Mass of solvent / Mass of solution) * 100

D) (Mass of solution / Mass of solute) * 100

42. If a solution contains 2 moles of solute A and 3 moles of solvent B, what is the mole fraction of solute A?

A) 2/3

B) 3/5

C) 2/5

D) 1/5

43. The sum of mole fractions of all components in a solution is always:

A) Less than 1

B) Greater than 1

C) Equal to 1

D) Zero

44. What is mole fraction of a component in a solution?

A) Moles of solvent / Moles of solute

B) Moles of solute / Moles of solution

C) Mass of solute / Mass of solution

D) Moles of solution / Moles of solute

45. A solution has a molarity of 2 M. What does this mean?

A) 2 moles of solute are present in 1 kg of solvent

B) 2 moles of solute are present in 1 liter of solvent

C) 2 moles of solute are present in 1 liter of solution

D) 2 grams of solute are present in 1 liter of solution

46. Which concentration unit changes with temperature?

A) Molality

B) Mole fraction

C) Molarity

D) Mass percentage

47. Molarity is defined as the number of moles of solute per:

A) Kilogram of solvent

B) Liter of solvent

C) Liter of solution

D) Kilogram of solution

48. If 1 mole of solute is dissolved in 1 kg of solvent, what is the molality of the solution?

A) 1 m

B) 0.1 m

C) 10 m

D) 0.5 m

49. Which concentration unit is independent of temperature?

A) Molarity

B) Molality

C) Percentage by volume

D) Normality

50. What is molality defined as?

A) Moles of solute per liter of solution

B) Moles of solute per kilogram of solvent

C) Mass of solute per liter of solution

D) Mass of solute per kilogram of solvent

Concentration expressions: molality molarity mole fraction percentage by volume and mass - Question Bank