Q: Which of the following is a plausible value for the rate of disappearance of $$A$$ from 40 to 60 s, given the reaction $$A \rightarrow B$$?

$$1.2 \times 10$$^{-2}$$\ \mathrm{M/s}$$

Question 1

Which equation correctly expresses the osmotic pressure ($$\Pi) of a $$solution in terms of molarity ($$M$$), the van't Hoff factor ($$i$$), the gas constant ($$R$$), and temperature ($$T$$)?

Accepted Answer

$$\Pi = iMRT$$

Question 2

A red blood cell is placed in a solution and begins to swell and eventually bursts. Which term best describes the solution relative to the cell, and what is the process called?

Accepted Answer

The solution is hypotonic; the process is hemolysis.

Question 3

Seawater contains 34 g of NaCl per liter. Given the molar mass of NaCl is 58.4 g/mol, and the density of seawater is 1.027 g/cm$$^3$$, what is the molality ($$m) of $$NaCl in seawater? (Assume 1 L solution.)

Accepted Answer

$$m = 0.586$$

Question 4

Which of the following best explains why water flows from the pure solvent side to the solution side across a semipermeable membrane during osmosis?

Accepted Answer

The solution side has a higher solute concentration, making it more stable, so water moves to dilute it.

Question 5

Calculate the freezing point depression ($$\Delta T_f) $$for seawater, given $$i = 2$$, $$K_f = 1.86\ ^\circ\mathrm{C}/m$$, and $$m = 0.586.$$

Accepted Answer

$$\Delta T_f = -2.2\ ^\circ\mathrm{C}$$

Question 6

A solution is prepared by dissolving 8.05 g of an unknown compound in 100 g of benzene, lowering the vapor pressure from 100 torr to 94.8 torr at 25$$^\circC. If $$the molar mass of benzene is 78.1 g/mol, what is the molar mass of the unknown compound?

Accepted Answer

$$115\ \mathrm{g/mol}$$

Question 7

Which of the following is NOT a characteristic of colloids?

Accepted Answer

Particles settle out on standing.

Question 8

Which of the following best describes the Tyndall Effect?

Accepted Answer

The scattering of light by colloidal particles.

Question 9

Which of the following is an example of a hydrophilic colloid?

Accepted Answer

Enzymes in water

Question 10

Which of the following statements about reaction rates is correct?

Accepted Answer

Increasing the temperature generally increases the reaction rate.

Question 11

Given the reaction $$A \rightarrow B$$, if the concentration of $$B$$ increases from 0.00 M to 0.46 M in 20 seconds, what is the average rate of appearance of $$B$$?

Accepted Answer

$$0.023\ \mathrm{M/s}$$

Question 12

Which of the following is a plausible value for the rate of disappearance of $$A$$ from 40 to 60 s, given the reaction $$A \rightarrow B$$?

Accepted Answer

$$1.2 	imes 10$$^{-2}$$\ \mathrm{M/s}$$

Question 13

Which of the following best describes reverse osmosis as used in water purification?

Accepted Answer

Applying pressure greater than the osmotic pressure to force water through a semipermeable membrane, leaving solutes behind.

Question 14

Which of the following mixtures is a colloid?

Accepted Answer

Milk

Question 15

Which of the following best explains why hydrophobic colloids can be stabilized in water?

Accepted Answer

By adsorbing ions on their surface, creating repulsion between particles.

Question 16

A colloidal dispersion is best described as:

Accepted Answer

A mixture with particles 5–1000 nm in size dispersed in another substance.

Question 17

Which of the following is a real-life application of the Tyndall Effect?

Accepted Answer

Using headlights in fog to see the beam of light.

Question 18

Which of the following is true about the rate of a chemical reaction?

Accepted Answer

It is always expressed as a positive quantity.

Question 19

Which of the following best describes the effect of a catalyst on a chemical reaction?

Accepted Answer

It increases the rate of the reaction without being consumed.

Colligative Properties, Colloids, and Reaction Rates: Study Notes for General Chemistry

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