Grade 12 : Chemistry - Solutions (Set 6)

Question 1

Calculate the osmotic pressure of a 0.05 M solution of $ ext{MgCl}_2$ at $27^\circ ext{C}$, assuming 80% dissociation. (Given $R = 0.0821 ext{ L atm mol}^{-1} ext{ K}^{-1}$).

Accepted Answer

C) 3.20 atm

Answer

A) 1.25 atm

Answer

B) 2.05 atm

Answer

D) 4.10 atm

Question 2

A non-volatile solute weighing 100 g is dissolved in 1000 g of water. The vapor pressure of the solution is 17.5 mm Hg at $20^\circ ext{C}$. If the vapor pressure of pure water at $20^\circ ext{C}$ is 17.535 mm Hg, calculate the molar mass of the solute. (Molar mass of water = 18 g/mol).

Accepted Answer

B) 180 g/mol

Answer

A) 168 g/mol

Answer

C) 200 g/mol

Answer

D) 225 g/mol

Question 3

A 0.2 molal aqueous solution of an unknown ionic compound $ ext{X}_3 ext{Y}_2$ has a boiling point of $100.208^\circ ext{C}$. Given $K_b$ for water is $0.52 ext{ K kg mol}^{-1}$, determine the degree of dissociation of $ ext{X}_3 ext{Y}_2$.

Accepted Answer

A) 25%

Answer

B) 50%

Answer

C) 75%

Answer

D) 100%

Question 4

A 0.1 M aqueous solution of a weak monoprotic acid $ ext{HA}$ freezes at $-0.20^\circ ext{C}$. If $K_f$ for water is $1.86 ext{ K kg mol}^{-1}$ and the density of the solution is 1 g/mL, calculate the percentage dissociation of the acid.

Accepted Answer

B) 7.5%

Answer

A) 5.5%

Answer

C) 10.0%

Answer

D) 12.5%

Question 5

The Henry's law constant for oxygen dissolved in water at $20^\circ ext{C}$ is $1.3 imes 10^{-3} ext{ mol L}^{-1} ext{ atm}^{-1}$. If oxygen constitutes 20% by volume of the air at 1 atm total pressure, what mass of oxygen (in mg) would be dissolved in 1 L of water at $20^\circ ext{C}$? (Molar mass of $ ext{O}_2 = 32 ext{ g/mol}$).

Accepted Answer

A) 8.32 mg

Answer

B) 10.4 mg

Answer

C) 13.0 mg

Answer

D) 2.6 mg

Question 6

A 16 M aqueous solution of $ ext{H}_2 ext{SO}_4$ has a density of 1.84 g/mL. Calculate the molality of the solution. (Molar mass of $ ext{H}_2 ext{SO}_4 = 98 ext{ g/mol}$).

Accepted Answer

D) 58.8 mol/kg

Answer

A) 16.0 mol/kg

Answer

B) 25.5 mol/kg

Answer

C) 48.3 mol/kg

Question 7

Which of the following pairs of liquids is expected to show a positive deviation from Raoult's Law?

Accepted Answer

D) Carbon disulfide and Acetone

Answer

A) Benzene and Toluene

Answer

B) Acetone and Chloroform

Answer

C) Nitric acid and Water

Answer

E) Water and Hydrochloric acid

Question 8

At 300 K, two liquids $ ext{X}$ and $ ext{Y}$ have pure vapor pressures $P^\circ_X = 100 ext{ mm Hg}$ and $P^\circ_Y = 200 ext{ mm Hg}$ respectively. If a solution is formed by mixing 2 moles of $ ext{X}$ and 3 moles of $ ext{Y}$, what is the total vapor pressure of the solution, assuming ideal behavior?

Accepted Answer

B) 160 mm Hg

Answer

A) 140 mm Hg

Answer

C) 175 mm Hg

Answer

D) 180 mm Hg

Question 9

Which statement correctly describes azeotropes?

Accepted Answer

C) Azeotropes are constant boiling mixtures that distill without change in composition.

Answer

A) Azeotropes are solutions that follow Raoult's Law over the entire range of composition.

Answer

B) Azeotropes are ideal solutions with a constant boiling point.

Answer

D) Azeotropes can be completely separated into their pure components by fractional distillation.

Question 10

200 mL of $0.5 m ext{NaCl}$ solution is mixed with 300 mL of $0.2 m ext{NaCl}$ solution. What is the final molarity of $ ext{NaCl}$ in the mixture? Assume volumes are additive.

Accepted Answer

B) 0.32 M

Answer

A) 0.28 M

Answer

C) 0.35 M

Answer

D) 0.40 M

Question 11

A solution contains 10% by mass of ethanol in water. If the density of the solution is 0.98 g/mL, what is the molarity of ethanol in the solution? (Molar mass of ethanol (C$_2$H$_5$OH) = 46 g/mol).

Accepted Answer

C) 2.13 M

Answer

A) 1.96 M

Answer

B) 2.05 M

Answer

D) 2.25 M