Q: A solution is prepared by dissolving 0.5 moles of NaCl in enough water to make 1.0 L of solution. What is the molarity ($$M) of $$the solution?

$$M = \frac{0.5}{1.0} = 0.5\ \text{M}$$

Q: A gas sample contains 2 moles of O$$_2$$ and 3 moles of N$$_2 in a 10 L $$container at 300 K. Using the ideal gas law, what is the total pressure in the container? ($$R = 0.08206\ \text{L atm} / \text{mol K})$$

$$P = \frac{(2 + 3) \times 0.08206 \times 300}{10} = 12.309\ \text{atm}$$

Question 1

Which of the following statements best explains why filtration cannot be used to separate a homogeneous mixture?

Accepted Answer

The components of a homogeneous mixture are uniformly distributed and cannot be separated by physical means like filtration.

Question 2

A solution is prepared by dissolving 0.5 moles of NaCl in enough water to make 1.0 L of solution. What is the molarity ($$M) of $$the solution?

Accepted Answer

$$M = \frac{0.5}{1.0} = 0.5\ 	ext{M}$$

Question 3

Which intermolecular force is present in all molecular substances, regardless of their polarity?

Accepted Answer

London dispersion forces

Question 4

A student mixes ethanol and water. Both substances dissolve completely in each other. Which principle best explains this observation?

Accepted Answer

Like dissolves like

Question 5

Which equation correctly relates the energy of a photon to its frequency?

Accepted Answer

$$E = h 
u$$

Question 6

If the wavelength of electromagnetic radiation increases, what happens to its frequency and energy?

Accepted Answer

Frequency and energy both decrease.

Question 7

A gas sample contains 2 moles of O$$_2$$ and 3 moles of N$$_2 in a 10 L $$container at 300 K. Using the ideal gas law, what is the total pressure in the container? ($$R = 0.08206\ 	ext{L atm} / 	ext{mol K})$$

Accepted Answer

$$P = \frac{(2 + 3) 	imes 0.08206 	imes 300}{10} = 12.309\ 	ext{atm}$$

Question 8

Which of the following best describes the Maxwell-Boltzmann distribution for a gas at higher temperature?

Accepted Answer

The distribution broadens and the average kinetic energy increases.

Question 9

Which intermolecular force is responsible for the unusually high boiling point of water?

Accepted Answer

Hydrogen bonding

Question 10

A mixture of gases contains 1 mole of CO$$_2$$, 2 moles of O$$_2$$, and 3 moles of N$$_2. $$What is the mole fraction of O$$_2 in $$the mixture?

Accepted Answer

$$X_{O_2$} = \frac{2}{1 + 2 + 3} = \frac{2}{6} = 0.333$$

Question 11

Which of the following statements about vapor pressure is correct?

Accepted Answer

Vapor pressure increases as temperature increases.

Question 12

Which property is most directly responsible for the pressure exerted by a gas in a container?

Accepted Answer

The collisions of gas particles with the walls of the container.

Question 13

Which of the following is NOT a type of intermolecular force?

Accepted Answer

Covalent bond

Question 14

A photon is absorbed by an atom, causing an electron to move from the ground state to an excited state. What happens to the energy of the atom?

Accepted Answer

The energy of the atom increases by an amount equal to the energy of the photon.

Question 15

Which of the following best explains why gases deviate from ideal behavior at high pressures?

Accepted Answer

Attractive forces between particles become significant at high pressure.

Question 16

Which equation is used to calculate the partial pressure of a gas in a mixture?

Accepted Answer

$$P_i = X_i P_{	ext{total}}$$

Question 17

Which of the following substances would have the highest vapor pressure at room temperature?

Accepted Answer

A liquid with weak London dispersion forces

Question 18

Which of the following is a correct statement about the relationship between average kinetic energy and temperature for a gas?

Accepted Answer

Average kinetic energy is directly proportional to temperature.

Question 19

Which of the following best describes the effect of increasing intermolecular forces on the boiling point of a liquid?

Accepted Answer

Boiling point increases.

Question 20

A sample of gas at 273 K and 1 atm is compressed to half its original volume at constant temperature. What happens to the pressure?

Accepted Answer

Pressure doubles.

Unit 3 AP CHEM

Guida di studio - Domande di pratica

Study guide - Flashcard