Q: A student calculates the solubility of oxygen in water at 25°C using $$k_H = 1.28 \times 10$$^{-3}$$ \ mol \ L$$^{-1}$$ \ $$atm^{-1}$$ and P$$_{$$O_2$$} = 0.21 \ atm$$. What is the solubility?

$$2.7 \times 10$$^{-4}$$ \ mol \ L$$^{-1}$$

Question 1

Which of the following best describes a saturated solution at a given temperature?

Accepted Answer

A solution in which the dissolved solute is in dynamic equilibrium with undissolved solute.

Question 2

Which of the following is an example of a solid solution?

Accepted Answer

Brass (copper and zinc)

Question 3

Which of the following statements about the energetics of solution formation is correct?

Accepted Answer

The process can be either endothermic or exothermic depending on the relative magnitudes of the energy changes involved.

Question 4

Given the following equation for the enthalpy of solution: $$\Delta H_{solution} = \Delta H_{solute} + \Delta H_{solvent} + \Delta H_{mix}$$, which term is typically exothermic?

Accepted Answer

$$\Delta H_{mix}$$

Question 5

Why are oil and water immiscible?

Accepted Answer

The interaction between nonpolar oil molecules and polar water molecules is very weak, making $$\Delta H_{solution}$$ large and positive.

Question 6

Which of the following compounds would be most soluble in benzene ($$C_6H_6$$)?

Accepted Answer

Iodine ($$I_2)$$

Question 7

Which of the following best explains why methanol ($$CH_3OH) is $$miscible with water?

Accepted Answer

Methanol can form hydrogen bonds with water molecules.

Question 8

Which of the following trends is observed as the hydrocarbon chain length increases in alcohols?

Accepted Answer

Solubility in water decreases.

Question 9

Which of the following statements about the enthalpy of hydration ($$\Delta H_{hydration}) is $$correct?

Accepted Answer

$$\Delta H_{hydration} is $$always exothermic.

Question 10

For an ionic compound, which equation correctly relates the enthalpy of solution to lattice energy and hydration energy?

Accepted Answer

$$\Delta H_{solution} = -\Delta H_{lattice} + \Delta H_{hydration}$$

Question 11

Which of the following factors increases the lattice energy of an ionic compound?

Accepted Answer

Increasing the magnitude of the ionic charges.

Question 12

A beaker containing ammonium nitrate ($$NH_4NO_3) $$and water becomes cold as the salt dissolves. What does this indicate about the dissolution process?

Accepted Answer

The process is endothermic.

Question 13

Which of the following best describes the effect of temperature on the solubility of most solid solutes in water?

Accepted Answer

Solubility increases with increasing temperature.

Question 14

Which of the following is an exception to the general trend of increasing solubility of solids with temperature, and what does this imply about $$\Delta H_{solution}$$?

Accepted Answer

Na_2SO_4; $$\Delta H_{solution} is $$exothermic.

Question 15

According to Henry’s Law, which equation correctly relates the solubility of a gas to its partial pressure?

Accepted Answer

$$S_{gas} = k_H P_{gas}$$

Question 16

A student calculates the solubility of oxygen in water at 25°C using $$k_H = 1.28 	imes 10$$^{-3}$$ \ mol \ L$$^{-1}$$ \ $$atm^{-1}$$ and P$$_{$$O_2$$} = 0.21 \ atm$$. What is the solubility?

Accepted Answer

$$2.7 	imes 10$$^{-4}$$ \ mol \ L$$^{-1}$$

Question 17

Which of the following best explains why $$Ca_3$$($$PO_4)_2$ is much less soluble in water than $$NaNO_3$$?

Accepted Answer

$$Ca_3$$($$PO_4)_2$ has a much higher lattice energy due to higher ionic charges.

Question 18

Which of the following statements about the solubility of gases in water is correct?

Accepted Answer

Gas solubility decreases with increasing temperature.

Question 19

Which of the following best describes the 'like dissolves like' rule?

Accepted Answer

Substances with similar intermolecular attractive forces will dissolve in each other.

Chapter 14: Solutions – Structure, Energetics, and Solubility

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