CHEM134 C003 Lesson 6 Quiz | Questions
and Answers – spring 2026 | 100% Correct -
American Public University
Section 1: Solution Concentration Units (6 Questions)
Q1: Which concentration unit is independent of temperature because it is based
on mass rather than volume?
A. Molarity
B. Molality [CORRECT]
C. Percent by volume
D. Molarity and percent by volume
Correct Answer: B
Rationale: Correct because molality (m = moles solute / kg solvent) uses mass of
solvent, which does not change with temperature, unlike molarity which depends
on solution volume.
Q2: A solution contains 15.0 g NaCl dissolved in 185.0 g water. What is the
percent by mass of NaCl in this solution?
A. 7.50%
B. 8.11% [CORRECT]
C. 8.50%
D. 12.3%
Correct Answer: B
Rationale: Correct because percent by mass = (15.0 g / (15.0 g + 185.0 g)) × 100%
= (15..0) × 100% = 7.50%; wait, recalculating: (15..0) × 100 = 7.50%.
Let me recalculate: 15..0 = 0.075 = 7.50%. The correct answer should be
7.50% which is option A. Let me fix this.
Correct Answer: A
Rationale: Correct because percent by mass = (mass solute / mass solution) ×
100% = (15.0 g / (15.0 g + 185.0 g)) × 100% = (15..0) × 100% = 7.50%.
, Q3: What is the mole fraction of ethanol (C₂H₅OH) in a solution containing 2.00
mol ethanol and 8.00 mol water?
A. 0.167
B. 0.200 [CORRECT]
C. 0.250
D. 0.800
Correct Answer: B
Rationale: Correct because mole fraction X_ethanol = moles ethanol / total moles
= 2.00 / (2.00 + 8.00) = 2..00 = 0.200.
Q4: A water sample contains 0.025 mg of lead per liter of solution. What is the
concentration in parts per billion (ppb)?
A. 2.5 ppb
B. 25 ppb [CORRECT]
C. 250 ppb
D. 0.25 ppb
Correct Answer: B
Rationale: Correct because for dilute aqueous solutions, 1 ppb ≈ 1 μg/L; 0.025 mg
= 25 μg, so concentration = 25 μg/L = 25 ppb.
Q5: Which of the following concentration units is most commonly used for
intravenous (IV) solutions in clinical settings?
A. Percent by mass
B. Molarity
C. Mass/volume percent (w/v) [CORRECT]
D. Mole fraction
Correct Answer: C
Rationale: Correct because mass/volume percent (g solute / 100 mL solution) is
the standard concentration unit for IV solutions, such as 0.9% NaCl (w/v) and 5%
dextrose (w/v).
Q6: A solution is prepared by dissolving 0.500 mol of glucose in 250.0 g of water.
What is the molality of this solution?
and Answers – spring 2026 | 100% Correct -
American Public University
Section 1: Solution Concentration Units (6 Questions)
Q1: Which concentration unit is independent of temperature because it is based
on mass rather than volume?
A. Molarity
B. Molality [CORRECT]
C. Percent by volume
D. Molarity and percent by volume
Correct Answer: B
Rationale: Correct because molality (m = moles solute / kg solvent) uses mass of
solvent, which does not change with temperature, unlike molarity which depends
on solution volume.
Q2: A solution contains 15.0 g NaCl dissolved in 185.0 g water. What is the
percent by mass of NaCl in this solution?
A. 7.50%
B. 8.11% [CORRECT]
C. 8.50%
D. 12.3%
Correct Answer: B
Rationale: Correct because percent by mass = (15.0 g / (15.0 g + 185.0 g)) × 100%
= (15..0) × 100% = 7.50%; wait, recalculating: (15..0) × 100 = 7.50%.
Let me recalculate: 15..0 = 0.075 = 7.50%. The correct answer should be
7.50% which is option A. Let me fix this.
Correct Answer: A
Rationale: Correct because percent by mass = (mass solute / mass solution) ×
100% = (15.0 g / (15.0 g + 185.0 g)) × 100% = (15..0) × 100% = 7.50%.
, Q3: What is the mole fraction of ethanol (C₂H₅OH) in a solution containing 2.00
mol ethanol and 8.00 mol water?
A. 0.167
B. 0.200 [CORRECT]
C. 0.250
D. 0.800
Correct Answer: B
Rationale: Correct because mole fraction X_ethanol = moles ethanol / total moles
= 2.00 / (2.00 + 8.00) = 2..00 = 0.200.
Q4: A water sample contains 0.025 mg of lead per liter of solution. What is the
concentration in parts per billion (ppb)?
A. 2.5 ppb
B. 25 ppb [CORRECT]
C. 250 ppb
D. 0.25 ppb
Correct Answer: B
Rationale: Correct because for dilute aqueous solutions, 1 ppb ≈ 1 μg/L; 0.025 mg
= 25 μg, so concentration = 25 μg/L = 25 ppb.
Q5: Which of the following concentration units is most commonly used for
intravenous (IV) solutions in clinical settings?
A. Percent by mass
B. Molarity
C. Mass/volume percent (w/v) [CORRECT]
D. Mole fraction
Correct Answer: C
Rationale: Correct because mass/volume percent (g solute / 100 mL solution) is
the standard concentration unit for IV solutions, such as 0.9% NaCl (w/v) and 5%
dextrose (w/v).
Q6: A solution is prepared by dissolving 0.500 mol of glucose in 250.0 g of water.
What is the molality of this solution?
