CHEM125 - QUIZ CHAPTERS 11/13 - NEW1

Quiz Chapters 11 and 13

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Question 1

In which of the following solvents will CO2 dissolve best?

Select one:

a. Ethanol, CH3CH2OH

b. Water, H2O

c. Acetone, CH3COCH3

d. Benzene, C6H6 Correct

Explanation

C6H6 is nonpolar so it dissolves with CO2 (nonpolar). Like dissolves like

Question 2

What happens to the water in a lake when it warms up in the summer?

Select one:

a. Viscosity of the water increases

b. The water in the lake evaporates faster Correct

c. Concentration of oxygen gas in the water increases

d. Surface tension of the water increases

Explanation

Adding heat to the lake makes the water phase change to vapor

Question 3

What happens when NaCl is added to water?

Select one:

a. The vapor pressure increases

b. The freezing point increases

c. The osmotic pressure decreases

d. The boiling point increases Correct

Explanation

An impure solution is going to have a lower melting point and higher boiling point.

Question 4

A certain liquid has a vapor pressure of 600 torr at room temperature. What will happen to the liquid if the atmospheric pressure will drop to 550 torr at the same temperature?

Select one:

a. The vapor pressure of the liquid will increase

b. The liquid will start boiling Correct

c. Nothing will happen

d. The vapor pressure of the liquid will drop to 550 torr

Explanation

If the vapor pressure is greater than atmospheric pressure then the liquid will start to boil faster.

Question 5

Which of the following compounds will have the highest boiling point?

Select one:

a. CO

b. H2CO

c. CH3OCH3

d. CH3OH

Explanation

CH3OH – hydrogen bond is present so there is a stronger bond between molecules, making the boiling point really high.

Question 6

Which of the following processes will be exothermic?

Select one:

a. Condensation of steam Correct

b. Sublimation of dry ice, CO2

c. Heating of water from 25°C to 75°C

d. Melting of ice

Explanation

Energy is being removed so gas transforms into a liquid state.

Question 7

What phase is stable at point G? CHEM125 - QUIZ CHAPTERS 11/13 - NEW1 1

Select one:

a. supercritical fluid

b. solid

c. gas

d. liquid

Explanation

Question 8

Which of the following graphs shows correctly the evolution of temperature (T) vs heat added (kJ), when 100 mL of water is heated starting from 50 °C to 150 ºC, at atmospheric pressure?

Select one:

Explanation

Liquid is heated from 50C to 100C
Liquid is transformed to steam at 100C
Steam is heated 100C to 150C

Question 9

Which of the following solutions will have the lowest freezing point?

Select one:

a. All three solutions will have the same freezing point

b. 1 mole of kitchen salt dissolved in 100 grams of water Correct

c. 1 mole of sugar dissolved in 100 grams of water

d. 1 mole of ethanol dissolved in 100 grams of water

Explanation

An impure solution has a low melting point. Think about putting salt on ice/ snow. Pure ice freezes at 32 F, but with salt the ice freeze at 20 F. So if the temp outside is 32 F and there is salt on the ice the ice will only freeze if the temp reaches 20F, otherwise the ice will melt at 32F.

Question 10

Which of the following liquids will have the highest vapor pressure at room temperature?

Select one:

a. CH2Cl2, boiling point = 40°C Correct

b. CH2I2, boiling point = 181°C

c. CHCl3, boiling point = 61°C

d. CCl4, boiling point = 76°C