Q: A sample contains $$3 \times 10$$^{23}$$ molecules in a volume of 0.5$$\ \text{L}$$. What is the number density?

$$6 \times 10$$^{23}$$\ \text{molecules/L}$$

Question 1

Which of the following best describes the behavior of atoms or molecules in a solid phase?

Accepted Answer

They are held together by strong spring-like bonds and can only vibrate or oscillate.

Question 2

During which phase change does a substance transition directly from a solid to a gas?

Accepted Answer

Sublimation

Question 3

Which property is shared by both solids and liquids, but not by gases?

Accepted Answer

They are nearly incompressible.

Question 4

A sample of gas is cooled until it reaches its condensation point. What phase change occurs?

Accepted Answer

Gas to liquid (condensation)

Question 5

Which of the following statements about temperature is correct?

Accepted Answer

Heat flows from the object with higher temperature to the one with lower temperature.

Question 6

What is the atomic mass number $$A of an $$atom with 8 protons and 10 neutrons?

Accepted Answer

$$A = 18$$

Question 7

Which of the following best describes the triple point of a substance?

Accepted Answer

The temperature and pressure where solid, liquid, and gas phases coexist in equilibrium.

Question 8

A container holds 2 moles of an ideal gas at a temperature of $$300\ 	ext{K}$$ and a pressure of $$1\ 	ext{atm}. $$What is the volume of the gas? (Use $$R = 0.0821\ 	ext{L}\cdot	ext{atm}/	ext{mol}\cdot	ext{K})$$

Accepted Answer

$$V = 49.3\ 	ext{L}$$

Question 9

Which process is represented by a vertical line on a pressure-volume ($$pV) $$diagram?

Accepted Answer

Isochoric process

Question 10

If a gas is compressed at constant temperature, which state variable must change according to the Ideal Gas Law?

Accepted Answer

Pressure

Question 11

Which of the following is true about the critical point in a phase diagram?

Accepted Answer

It is the point where gas and liquid phases become indistinguishable.

Question 12

A sample of water is heated from $$20\ ^\circ	ext{C} to$$ $$100\ ^\circ	ext{C}$$, then boiled at $$100\ ^\circ	ext{C}. $$What happens to the temperature during the boiling process?

Accepted Answer

It remains constant.

Question 13

Which of the following is NOT a state variable used to describe a gas in the Ideal Gas Law?

Accepted Answer

Atomic mass number ($$A)$$

Question 14

A gas undergoes an isobaric process. If the volume increases, what must happen to the temperature?

Accepted Answer

Temperature must increase.

Question 15

Which of the following statements about the Kelvin scale is correct?

Accepted Answer

0 K is absolute zero, where all atomic motion stops.

Question 16

If a substance is cooled to its melting/freezing point, which two phases are in equilibrium?

Accepted Answer

Solid and liquid

Question 17

Which of the following best describes a quasi-static process?

Accepted Answer

A process that happens slowly enough that the system remains close to thermal equilibrium.

Question 18

A sample contains $$3 	imes 10$$^{23}$$ molecules in a volume of 0.5$$\ 	ext{L}$$. What is the number density?

Accepted Answer

$$6 	imes 10$$^{23}$$\ 	ext{molecules/L}$$

Question 19

Which statement about the atomic mass unit (amu) is correct?

Accepted Answer

1 amu is exactly 1/12 the mass of a carbon-12 nucleus.

Question 20

Which phase is most easily compressible and often more than a thousand times less dense than solids or liquids?

Accepted Answer

Gas

A Macroscopic Description of Matter: Phases, State Variables, and the Ideal Gas Law

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