Chemistry Test Solutions 3 — Questions and Answers
Question 1: Osmosis is best defined as the movement of:
- Solute from low to high concentration through a semipermeable membrane
- Solvent from high to low solute concentration through a semipermeable membrane
- Solvent from low to high solute concentration through a semipermeable membrane (Correct answer)
- Both solute and solvent through a semipermeable membrane
Correct answer: Solvent from low to high solute concentration through a semipermeable membrane
Osmosis is the net movement of solvent (typically water) from a region of lower solute concentration to higher solute concentration through a semipermeable membrane.
Question 2: If the osmotic pressure of a solution at 25°C is 2.46 atm, and R = 0.0821 L·atm/mol·K, what is the molar concentration of the solute?
- 0.05 M
- 0.10 M (Correct answer)
- 0.20 M
- 0.50 M
Correct answer: 0.10 M
Using π = MRT: M = π/(RT) = 2.46 / (0.0821 × 298) = 0.10 M.
Question 3: Which solution has the highest osmotic pressure at the same temperature?
- 0.1 M glucose
- 0.1 M NaCl
- 0.1 M CaCl₂ (Correct answer)
- 0.1 M sucrose
Correct answer: 0.1 M CaCl₂
CaCl₂ dissociates into 3 ions (i=3), giving the highest effective particle concentration and thus the highest osmotic pressure.
Question 4: A red blood cell placed in a hypertonic solution will:
- Swell and burst (lyse)
- Remain unchanged
- Shrink (crenate) (Correct answer)
- Divide
Correct answer: Shrink (crenate)
In a hypertonic solution, water leaves the cell by osmosis toward the higher external solute concentration, causing the cell to shrink (crenation).
Question 5: Reverse osmosis requires:
- A pressure lower than osmotic pressure applied to the concentrated solution
- A pressure greater than osmotic pressure applied to the concentrated solution (Correct answer)
- Heating the concentrated solution
- A non-semipermeable membrane
Correct answer: A pressure greater than osmotic pressure applied to the concentrated solution
Reverse osmosis forces solvent from the concentrated side to the dilute side by applying external pressure exceeding the osmotic pressure.
Question 6: Which of the following is an example of a colligative property?
- Electrical conductivity of the solution
- Color change of the solution
- Freezing point depression (Correct answer)
- Reaction rate in solution
Correct answer: Freezing point depression
Freezing point depression depends only on the number of dissolved particles, not their identity, making it a colligative property.
Question 7: The freezing point depression constant (Kf) for water is 1.86 °C/m. What is the freezing point of a 2.0 m sucrose solution?
- -1.86 °C
- -2.0 °C
- -3.72 °C (Correct answer)
- -0.93 °C
Correct answer: -3.72 °C
ΔTf = Kf × m × i = 1.86 × 2.0 × 1 = 3.72 °C, so the freezing point is 0 − 3.72 = −3.72 °C.
Chemistry Test Solutions 3
Osmosis is best defined as the movement of: