Question 1

Which of the following best explains why the solubility of oxygen in water decreases as temperature increases, as shown in the first image?

Accepted Answer

Higher temperatures increase the kinetic energy of gas molecules, making them more likely to escape from the liquid phase.

Question 2

Refer to the second image. What real-world consequence is depicted in image (b) that results from the decreased solubility of oxygen in water at higher temperatures?

Accepted Answer

Thermal pollution leads to fish kills due to insufficient dissolved oxygen.

Question 3

The third image shows Lake Nyos before and after a controlled venting event. What chemical principle explains the catastrophic release of CO$$_2$$ from the lake in 1986?

Accepted Answer

A sudden decrease in pressure caused dissolved CO$$_2 to $$rapidly come out of solution, similar to opening a carbonated beverage.

Question 4

The fourth image shows a bottle of antifreeze/coolant. Which property of solutions is most relevant to the function of antifreeze in a car's cooling system?

Accepted Answer

Freezing point depression, which prevents the coolant from freezing at low temperatures.

Question 5

Based on the fifth image, which compound shows the greatest increase in solubility with temperature?

Accepted Answer

KNO$$_3$$

Question 6

A solution is prepared by dissolving 0.5 mol of NaCl in 1 kg of water. What is the molality ($$m) of $$the solution? $$m = \frac{	ext{moles of solute}}{	ext{kg of solvent}}$$

Accepted Answer

$$0.5\ m$$

Question 7

Which of the following best describes the process shown in the sixth image, where solvent moves through a semipermeable membrane?

Accepted Answer

Osmosis, where solvent moves from an area of lower solute concentration to higher solute concentration.

Question 8

Which equation correctly expresses the osmotic pressure ($$\pi) of a $$solution? (R = 0.08206 L·atm/mol·K, T in K, M = molarity)

Accepted Answer

$$\pi = MRT$$

Question 9

Refer to the seventh image. Which colligative property is being used to determine the molar mass of an unknown compound?

Accepted Answer

Freezing point depression ($$\Delta T_f)$$

Question 10

A student dissolves 10 g of NaCl in 100 g of water and observes a decrease in the freezing point. Which step is necessary to calculate the new freezing point, as shown in the eighth image?

Accepted Answer

Calculate the molality of the solution.

Question 11

Which of the following statements about the van’t Hoff factor ($$i) is $$correct?

Accepted Answer

It represents the number of particles a solute produces in solution relative to the number of formula units dissolved.

Question 12

Which of the following best explains why strong electrolytes have a greater effect on colligative properties than non-electrolytes at the same concentration?

Accepted Answer

Strong electrolytes dissociate into more particles, increasing the total solute particle concentration.

Question 13

Which of the following mixtures is a colloid, as shown in the ninth image?

Accepted Answer

Milk

Question 14

Which of the following best describes why oil and water are immiscible?

Accepted Answer

Oil is nonpolar and water is polar, so their intermolecular forces are not compatible.

Question 15

Which of the following is an example of a real-life application of freezing point depression?

Accepted Answer

Spreading salt on icy roads to melt ice.

Question 16

Which equation represents Raoult’s Law for the vapor pressure of a solution?

Accepted Answer

$$P_{	ext{solution}} = X_{	ext{solvent}} P^*_{	ext{solvent}}$$

Question 17

A solution is prepared by mixing 2 mol ethanol and 3 mol water. What is the mole fraction of ethanol ($$X_{	ext{ethanol}}$$)?

Accepted Answer

$$X_{	ext{ethanol}} = \frac{2}{2+3} = 0.4$$

Question 18

Which of the following best describes the Tyndall effect, a property of colloids?

Accepted Answer

The scattering of light by colloidal particles, making beams of light visible.

Solutions and Their Properties: Structure, Solubility, and Colligative Effects

Guida di studio - Domande di pratica

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