Q: A solution is made by dissolving 10 g of Na$$_2SO$_4 in 1 kg of $$water. Which equation would you use to calculate the new vapor pressure of the solution?

$$P_{solution} = \frac{mol_{solvent}}{mol_{solvent} + i \times mol_{solute}} P^0$_{solvent}$$

Q: A solution is prepared by dissolving 5 g of NaCl in 850 g of CCl$$_4. $$The freezing point depression constant ($$K_f) $$for CCl$$_4 is 29.9$$ $$^\circC/m$$, and the Van’t Hoff factor ($$i) $$for NaCl is 1.9. What is the correct formula to calculate the freezing point depression ($$\Delta T_f$$)?

$$\Delta T_f = i \times K_f \times m$$

Q: Which of the following equations correctly represents the boiling point elevation for a solution?

$$\Delta T_b = i \times K_b \times m$$

Question 1

Which of the following best describes a colligative property?

Accepted Answer

A property that depends only on the number of solute particles present, not their identity.

Question 2

When NaCl dissolves in water, it dissociates completely. What is the theoretical Van’t Hoff factor ($$i) $$for NaCl?

Accepted Answer

$$i = 2$$

Question 3

Which of the following compounds will have a Van’t Hoff factor ($$i) of 3 $$when dissolved in water?

Accepted Answer

K$$_2SO$_4$$

Question 4

A solution is made by dissolving 10 g of Na$$_2SO$_4 in 1 kg of $$water. Which equation would you use to calculate the new vapor pressure of the solution?

Accepted Answer

$$P_{solution} = \frac{mol_{solvent}}{mol_{solvent} + i 	imes mol_{solute}} P^0$_{solvent}$$

Question 5

Which of the following statements about polyatomic ions is correct?

Accepted Answer

Polyatomic ions never split apart when ionic compounds dissolve in water.

Question 6

A solution is prepared by dissolving 5 g of NaCl in 850 g of CCl$$_4. $$The freezing point depression constant ($$K_f) $$for CCl$$_4 is 29.9$$ $$^\circC/m$$, and the Van’t Hoff factor ($$i) $$for NaCl is 1.9. What is the correct formula to calculate the freezing point depression ($$\Delta T_f$$)?

Accepted Answer

$$\Delta T_f = i 	imes K_f 	imes m$$

Question 7

Which of the following best explains why the boiling point of water increases when NaCl is added?

Accepted Answer

The NaCl decreases the vapor pressure of water, requiring a higher temperature to boil.

Question 8

If you dissolve 1 mole of MgCl$$_2 in $$water, what is the theoretical Van’t Hoff factor ($$i) $$for this solute?

Accepted Answer

$$i = 3$$

Question 9

Which of the following is NOT a colligative property?

Accepted Answer

Density of the solute

Question 10

A student adds 0.5 mol of glucose (C$$_6H$_{12}O$_6) to 1 kg of $$water. What is the Van’t Hoff factor ($$i) $$for glucose?

Accepted Answer

$$i = 1$$

Question 11

Which of the following best describes the effect of adding a non-volatile solute to a solvent?

Accepted Answer

It decreases the vapor pressure of the solvent.

Question 12

A solution is made by dissolving 1 mol of K$$_3PO$_4 in $$water. What is the theoretical Van’t Hoff factor ($$i) $$for K$$_3PO$_4$$?

Accepted Answer

$$i = 4$$

Question 13

Which of the following equations correctly represents the boiling point elevation for a solution?

Accepted Answer

$$\Delta T_b = i 	imes K_b 	imes m$$

Question 14

A solution of 0.2 mol Na$$_2SO$_4 is $$prepared in 1 kg of water. What is the total number of moles of ions produced upon complete dissociation?

Accepted Answer

0.6 mol

Question 15

Which of the following best explains why antifreeze (ethylene glycol) is added to car radiators in winter?

Accepted Answer

It lowers the freezing point of water, preventing it from freezing.

Question 16

A solution is made by dissolving 1 mol of (NH$$_4$$)$$_2SO$_4 in $$water. What is the theoretical Van’t Hoff factor ($$i) $$for this compound?

Accepted Answer

$$i = 3$$

Question 17

Which of the following would result in the greatest freezing point depression for 1 kg of water?

Accepted Answer

1 mol of CaCl$$_2$$

Question 18

If the vapor pressure of pure water at 40$$^\circC is 55.3 $$torr, what happens to the vapor pressure when a non-volatile solute is added?

Accepted Answer

It decreases below 55.3 torr.

Question 19

Which of the following best describes the effect of adding an ionic compound to water on the hydrogen bonding between water molecules?

Accepted Answer

It disrupts hydrogen bonding by introducing ion-dipole interactions.

Question 20

A solution is made by dissolving 1 mol of Fe$$_2(SO$_4$$)$$_3 in $$water. What is the theoretical Van’t Hoff factor ($$i) $$for this compound?

Accepted Answer

$$i = 5$$

CH 11

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