Grade 12 : Chemistry - Solutions (Set 8)

Question 1

A 5% (w/v) aqueous solution of a non-electrolyte has an osmotic pressure of 4.92 atm at $27^{\circ} ext{C}$. What is the approximate molar mass of the solute? (Given: $R = 0.082 ext{ L atm mol}^{-1} ext{ K}^{-1}$)

Accepted Answer

B) 250 g/mol

Answer

A) 120 g/mol

Answer

C) 300 g/mol

Answer

D) 600 g/mol

Question 2

A solution containing 18 g of glucose ($C_6H_{12}O_6$) in 100 g of water boils at $100.52^{\circ} ext{C}$. If $K_b$ for water is $0.52 ext{ K kg mol}^{-1}$, what is the theoretical boiling point elevation, and how does it compare to the observed value?

Accepted Answer

B) Theoretical $\Delta T_b = 0.52^{\circ}	ext{C}$, observed matches theoretical.

Answer

A) Theoretical $\Delta T_b = 0.26^{\circ}	ext{C}$, observed is lower due to impurities.

Answer

C) Theoretical $\Delta T_b = 0.52^{\circ}	ext{C}$, observed is higher due to impurities.

Answer

D) Theoretical $\Delta T_b = 1.04^{\circ}	ext{C}$, observed is higher due to association.

Question 3

At $25^{\circ} ext{C}$, the vapor pressure of pure benzene ($C_6H_6$) is 100 torr and that of pure toluene ($C_7H_8$) is 30 torr. A solution is prepared by mixing 78 g of benzene and 92 g of toluene. Assuming ideal behavior, what is the vapor pressure of the solution at $25^{\circ} ext{C}$? (Atomic masses: C=12, H=1)

Accepted Answer

B) 65 torr

Answer

A) 70 torr

Answer

C) 50 torr

Answer

D) 35 torr

Question 4

A solution contains 0.1 mol of NaCl and 0.1 mol of $MgCl_2$ in 1 kg of water. Given $K_f = 1.86 ext{ K kg mol}^{-1}$ for water, what is the freezing point of the solution? (Assume complete dissociation)

Accepted Answer

A) $-0.93^{\circ}	ext{C}$

Answer

B) $-0.558^{\circ}	ext{C}$

Answer

C) $-0.372^{\circ}	ext{C}$

Answer

D) $-0.186^{\circ}	ext{C}$

Question 5

The Henry's Law constant for oxygen ($O_2$) dissolved in water is $1.3 imes 10^{-3} ext{ mol L}^{-1} ext{ atm}^{-1}$ at $25^{\circ} ext{C}$. If the partial pressure of oxygen in the air is 0.21 atm, what is the concentration of dissolved oxygen in water at $25^{\circ} ext{C}$?

Accepted Answer

A) $2.73 	imes 10^{-4} 	ext{ mol L}^{-1}$

Answer

B) $6.19 	imes 10^{-3} 	ext{ mol L}^{-1}$

Answer

C) $1.3 	imes 10^{-3} 	ext{ mol L}^{-1}$

Answer

D) $2.1 	imes 10^{-4} 	ext{ mol L}^{-1}$

Question 6

An aqueous solution of $H_2SO_4$ is 2.0 M and has a density of 1.10 g/mL. Calculate the molality of the solution. (Molar mass of $H_2SO_4 = 98 ext{ g/mol}$)

Accepted Answer

D) 2.21 mol/kg

Answer

A) 1.82 mol/kg

Answer

B) 2.00 mol/kg

Answer

C) 2.08 mol/kg

Question 7

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

Accepted Answer

D) Ethanol and Cyclohexane

Answer

A) Benzene and Toluene

Answer

B) Acetone and Chloroform

Answer

C) Ethanol and Water

Answer

E) n-Hexane and n-Heptane

Question 8

A 100 mL solution of $0.2 M HCl$ is mixed with 150 mL of $0.1 M NaOH$. What is the final concentration of NaCl in the resulting solution?

Accepted Answer

B) 0.06 M

Answer

A) 0.04 M

Answer

C) 0.08 M

Answer

D) 0.10 M

Question 9

A 0.01 M aqueous solution of potassium ferrocyanide ($K_4[Fe(CN)_6]$) has a freezing point of $-0.0744^{\circ} ext{C}$. Calculate its apparent degree of dissociation. (Given: $K_f = 1.86 ext{ K kg mol}^{-1}$ for water).

Accepted Answer

C) 0.75

Answer

A) 0.50

Answer

B) 0.60

Answer

D) 1.00

Question 10

Which of the following statements is true regarding azeotropic mixtures?

Accepted Answer

C) They boil at a constant temperature, and their vapor phase has the same composition as their liquid phase.

Answer

A) They can be completely separated into pure components by fractional distillation.

Answer

B) They always show positive deviation from Raoult's law.

Answer

D) The vapor pressure of an azeotropic mixture is always intermediate between that of its pure components.

Question 11

What is the mole fraction of glucose ($C_6H_{12}O_6$) in a $20% (w/w)$ aqueous solution? (Molar mass of glucose = 180 g/mol, water = 18 g/mol)

Accepted Answer

A) 0.0227

Answer

B) 0.0250

Answer

C) 0.0400

Answer

D) 0.0200

Question 12

What is the mole fraction of glucose ($C_6H_{12}O_6$) in a $20% (w/w)$ aqueous solution? (Molar mass of glucose = 180 g/mol, water = 18 g/mol)

Accepted Answer

A) 0.0244

Answer

B) 0.0227

Answer

C) 0.0400

Answer

D) 0.0200

Question 13

A non-volatile solute 'X' is added to a solvent. The vapor pressure of the solution is 80% of the vapor pressure of the pure solvent at $30^{\circ} ext{C}$. What is the mole fraction of the solute in the solution?

Accepted Answer

A) 0.20

Answer

B) 0.80

Answer

C) 0.25

Answer

D) 0.75

Question 14

Which of the following describes a solution that exhibits negative deviation from Raoult's Law?

Accepted Answer

C) Acetone and Chloroform, where hydrogen bonding forms between components.

Answer

A) Benzene and Toluene, where intermolecular forces are similar.

Answer

B) Ethanol and Cyclohexane, where new interactions are weaker than original ones.

Answer

D) Carbon disulfide and Acetone, where interactions are weaker than pure components.

Set 8Grade 12 : Chemistry - Solutions