Q: A solution contains 100 ppm of lead (Pb, MW = 207.2 g/mol). What is the molarity of this solution?

$4.83 \times 10^{-4}\ \mathrm{M}$

Q: If the 100 ppm Pb solution is prepared by dissolving Pb(NO$_3$)$_2$ in water, what is the molarity of NO$_3^-$ ions in the solution?

$9.66 \times 10^{-4}\ \mathrm{M}$

Q: A 0.070 g sample of insulin is dissolved in 10.0 mL water, giving an osmotic pressure of 23 torr at 25°C. What is the molar mass of insulin? (Use $R = 0.0821\ \mathrm{L\ atm\ mol^{-1}\ K^{-1}}$, $T = 298\ \mathrm{K}$, $1\ \mathrm{atm} = 760\ \mathrm{torr}$)

$5.7 \times 10^{3}\ \mathrm{g/mol}$

Question 1

A solution contains 100 ppm of lead (Pb, MW = 207.2 g/mol). What is the molarity of this solution?

Accepted Answer

$4.83 	imes 10^{-4}\ \mathrm{M}$

Question 2

If the 100 ppm Pb solution is prepared by dissolving Pb(NO$_3$)$_2$ in water, what is the molarity of NO$_3^-$ ions in the solution?

Accepted Answer

$9.66 	imes 10^{-4}\ \mathrm{M}$

Question 3

An environmental chemist dissolves 0.238 mg of dirt in water to make a solution. Which unit is most appropriate to describe the concentration?

Accepted Answer

Part per million (ppm)

Question 4

A solution contains 0.0047 g of SO$_2$ (MW = 64.1 g/mol) per liter. What is the concentration of SO$_2$ in ppm?

Accepted Answer

$4.7\ \mathrm{ppm}$

Question 5

Which of the following best describes the effect of adding a nonvolatile solute to a solvent?

Accepted Answer

The vapor pressure of the solution decreases compared to the pure solvent.

Question 6

Which equation correctly expresses Raoult’s Law for vapor pressure lowering?

Accepted Answer

$P_{\mathrm{solution}} = X_{\mathrm{solvent}} P^{\circ}_{\mathrm{solvent}}$

Question 7

A solution is made by mixing 25.0 g heptane (MW = 100 g/mol, $P^{\circ} = 791$ torr) and 35.0 g octane (MW = 114 g/mol, $P^{\circ} = 352$ torr). What is the total vapor pressure above the solution?

Accepted Answer

$P_{\mathrm{total}} = X_{\mathrm{heptane}} P^{\circ}_{\mathrm{heptane}} + X_{\mathrm{octane}} P^{\circ}_{\mathrm{octane}}$

Question 8

Which colligative property is responsible for the phenomenon of salting icy roads in winter?

Accepted Answer

Freezing point depression

Question 9

What is the boiling point elevation ($\Delta T_b$) for a solution containing 1.500 g NaCl in 0.2500 kg H$_2$O? ($K_b = 0.512\ ^\circ\mathrm{C}/m$, NaCl $i=2$)

Accepted Answer

$0.104\ ^\circ\mathrm{C}$

Question 10

Which equation is used to calculate the freezing point depression of a solution?

Accepted Answer

$\Delta T_f = K_f i m$

Question 11

A 0.3 m aqueous NaCl solution is prepared. What is the expected van’t Hoff factor ($i$) for NaCl?

Accepted Answer

$i = 2$

Question 12

Which of the following statements about colligative properties is correct?

Accepted Answer

They depend on the number of solute particles, not their identity.

Question 13

Which equation is used to calculate the osmotic pressure of a solution?

Accepted Answer

$\Pi = MRT$

Question 14

A 0.070 g sample of insulin is dissolved in 10.0 mL water, giving an osmotic pressure of 23 torr at 25°C. What is the molar mass of insulin? (Use $R = 0.0821\ \mathrm{L\ atm\ mol^{-1}\ K^{-1}}$, $T = 298\ \mathrm{K}$, $1\ \mathrm{atm} = 760\ \mathrm{torr}$)

Accepted Answer

$5.7 	imes 10^{3}\ \mathrm{g/mol}$

Question 15

Which type of colloid is formed when gas is dispersed in a liquid?

Accepted Answer

Foam

Question 16

What is the Tyndall effect?

Accepted Answer

The scattering of visible light by colloidal particles

Question 17

Which statement best explains why surfactants (soaps) can dissolve oil in water?

Accepted Answer

They contain both hydrophobic and hydrophilic components, allowing them to form micelles.

Question 18

Which of the following is NOT a colligative property?

Accepted Answer

Density

Question 19

A solution is hypotonic compared to a cell. What will happen to the cell?

Accepted Answer

Water will enter the cell, causing it to swell.

Question 20

Why does adding salt to vegetables help release moisture from them?

Accepted Answer

Salt increases the osmotic pressure outside the vegetable cells, causing water to move out.

Solutions and Colligative Properties: Concentration Units, Vapor Pressure, and Related Effects

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