Solutions Chapter-Wise Test 16

Correct answer Carries: 4.

Wrong Answer Carries: -1.

What is the molarity of a solution containing 9 g of glucose (molar mass = 180 g/mol) in 500 mL of solution?

Moles of glucose = \( \frac{9}{180} = 0.05 \, \text{mol} \).

Volume = 500 mL = 0.5 L.

Molarity = \( \frac{0.05}{0.5} = 0.1 \, \text{M} \).

0.1 M
0.2 M
0.05 M
1.0 M
1

A solution of 10 g of a non-volatile solute in 400 g of water has a boiling point elevation of 0.13°C. What is the molar mass of the solute? (\( K_b = 0.52 \, \text{K kg mol}^{-1} \))

\( \Delta T_b = K_b \cdot m \).

\( 0.13 = 0.52 \times \frac{\text{moles}}{0.4} \).

Moles = \( \frac{0.13 \times 0.4}{0.52} = 0.1 \).

Molar mass = \( \frac{10}{0.1} = 100 \, \text{g/mol} \).

90 g/mol
100 g/mol
110 g/mol
95 g/mol
2

How many grams of KCl (molar mass = 74.5 g/mol) are needed to prepare 250 mL of a 0.4 M solution?

Moles of KCl = \( 0.4 \times 0.25 = 0.1 \, \text{mol} \).

Mass = \( 0.1 \times 74.5 = 7.45 \, \text{g} \).

7.0 g
7.45 g
8.0 g
6.5 g
2

A solution is prepared with 46 g of ethanol (molar mass = 46 g/mol) and 54 g of water. If the mole fraction of ethanol becomes 0.4 after adding more ethanol, what mass of ethanol was added?

Initial moles of ethanol = \( \frac{46}{46} = 1 \).

Moles of water = \( \frac{54}{18} = 3 \).

Let additional moles of ethanol = \( x \).

New mole fraction = \( \frac{1 + x}{1 + x + 3} = 0.4 \).

\( 1 + x = 0.4 (4 + x) \), \( 1 + x = 1.6 + 0.4x \), \( 0.6x = 0.6 \), \( x = 1 \).

Mass added = \( 1 \times 46 = 46 \, \text{g} \).

46 g
50 g
40 g
48 g
1

A solution of two volatile liquids has vapor pressures of 180 mm Hg and 240 mm Hg for pure components. If the total vapor pressure is 216 mm Hg, what is the mole fraction of the second component?

\( P = P_1^0 \cdot x_1 + P_2^0 \cdot x_2 \), where \( x_1 + x_2 = 1 \).

\( 216 = 180 (1 - x_2) + 240 x_2 \).

\( 216 = 180 - 180 x_2 + 240 x_2 \).

\( 216 - 180 = 60 x_2 \), \( x_2 = \frac{36}{60} = 0.6 \).

0.5
0.6
0.4
0.7
2

A solution contains 32 g of methanol (molar mass = 32 g/mol) and 90 g of water. If the mole fraction of methanol is to be increased to 0.3 by adding methanol, what mass of methanol is added?

Initial moles of methanol = \( \frac{32}{32} = 1 \).

Moles of water = \( \frac{90}{18} = 5 \).

Let additional moles of methanol = \( x \).

New mole fraction = \( \frac{1 + x}{1 + x + 5} = 0.3 \).

\( 1 + x = 0.3 (6 + x) \), \( 1 + x = 1.8 + 0.3x \), \( 0.7x = 0.8 \), \( x \approx 1.1429 \).

Mass added = \( 1.1429 \times 32 \approx 36.57 \, \text{g} \).

36.57 g
40 g
35 g
38 g
1

A solution contains 9 g of a solute (molar mass = 90 g/mol) in 450 mL of solution. What is the molarity?

Moles of solute = \( \frac{9}{90} = 0.1 \, \text{mol} \).

Volume = 450 mL = 0.45 L.

Molarity = \( \frac{0.1}{0.45} \approx 0.2222 \, \text{M} \).

0.2 M
0.2222 M
0.25 M
0.18 M
2

A 0.2 molal solution of a solute in water has a freezing point depression of 0.744°C. If the solute dissociates into 2 ions, what is the degree of dissociation? (\( K_f = 1.86 \, \text{K kg mol}^{-1} \))

\( \Delta T_f = i \cdot K_f \cdot m \).

\( 0.744 = i \times 1.86 \times 0.2 \).

\( i = \frac{0.744}{1.86 \times 0.2} = 2 \).

\( i = 1 + \alpha (n - 1) \), \( 2 = 1 + \alpha (2 - 1) \), \( \alpha = 1 \).

0.8
0.9
0.95
1
4

What is the mass percentage of a solution if 5 g of a solute is dissolved in 45 g of water?

Total mass = 5 g + 45 g = 50 g.

Mass % = \( \frac{5}{50} \times 100 = 10\% \).

5%
8%
10%
12%
3

What is the osmotic pressure of a 0.02 M solution of a non-electrolyte at 27°C? (\( R = 0.0821 \, \text{L atm mol}^{-1} \text{K}^{-1} \))

\( \Pi = MRT \).

\( \Pi = 0.02 \times 0.0821 \times 300 \approx 0.492 \, \text{atm} \).

0.4 atm
0.45 atm
0.492 atm
0.5 atm
3

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