Q: A sealed container holds $$100 g of$$ $$O_2$$ gas. How many moles and molecules does it contain? (Molar mass of $$O_2 is$$ $$32 g/$$mol, Avogadro's number $$N_A = 6.02 \times 10$$^{23}$$)

$$3.1$$ mol, $$1.9 \times 10$$^{24}$$ molecules

Question 1

Which statement best describes the second law of thermodynamics?

Accepted Answer

The entropy of an isolated system never decreases.

Question 2

A sealed, rigid container holds a fixed amount of gas. If the temperature increases from $$100\ ^\circ\mathrm{C} to$$ $$200\ ^\circ\mathrm{C}$$, by what factor does the pressure increase?

Accepted Answer

1.3

Question 3

Which equation correctly expresses the ideal-gas law in terms of the number of molecules $$N$$?

Accepted Answer

$$pV = Nk$$_{B}$$T$$

Question 4

A car tire is inflated to a gauge pressure of $$30.0$$ psi at $$0\ ^\circ\mathrm{C}. On a $$hot day, the temperature inside the tire rises to $$30\ ^\circ\mathrm{C}. $$What is the new gauge pressure, assuming the volume is constant?

Accepted Answer

$$34.9$$ psi

Question 5

Which of the following is true about the molecular speeds in a gas at a given temperature?

Accepted Answer

The root-mean-square speed is the speed of a typical atom.

Question 6

What is the change in height of a $$180 m $$steel tower when the temperature increases from $$0\ ^\circ\mathrm{C} to$$ $$30\ ^\circ\mathrm{C}$$? (Coefficient of linear expansion for steel: $$\alpha = 12 	imes 10$$^{-6}$$\ \mathrm{K}^{-1})$$

Accepted Answer

$$0.065 m$$

Question 7

Which process is characterized by $$Q = 0 (no $$heat transfer)?

Accepted Answer

Adiabatic process

Question 8

A sealed container holds $$100 g of$$ $$O_2$$ gas. How many moles and molecules does it contain? (Molar mass of $$O_2 is$$ $$32 g/$$mol, Avogadro's number $$N_A = 6.02 	imes 10$$^{23}$$)

Accepted Answer

$$3.1$$ mol, $$1.9 	imes 10$$^{24}$$ molecules

Question 9

Which of the following statements about heat engines is correct?

Accepted Answer

No heat engine can be 100% efficient.

Question 10

What is the root-mean-square speed $$v_{rms} of a $$nitrogen molecule ($$N_2) at$$ $$178 K$$? (Molecular mass $$m = 28 u$$, $$1 u$$ $$= 1.66 	imes 10$$^{-27}$$ kg, k_B = 1.38$$ 	imes $$10^{-23} J/K)$$

Accepted Answer

$$400 m/s$$

Question 11

Which formula gives the work done by a gas during a constant-pressure process?

Accepted Answer

$$W = p(V_f - V_i)$$

Question 12

A heat pump is used to cool a room. Which statement about its coefficient of performance (COP) is correct?

Accepted Answer

COP for cooling is $$\frac{Q_C}{W}$$, and is always less than for heating.

Question 13

Which of the following is the correct definition of pressure in a gas?

Accepted Answer

$$P = \frac{F}{A}$$

Question 14

A $$1$$ mole sample of an ideal gas at $$0\ ^\circ\mathrm{C}$$ and $$1.00$$ atm occupies what volume?

Accepted Answer

$$22.4 L$$

Question 15

Which equation describes the change in thermal energy of an ideal gas in terms of temperature change?

Accepted Answer

$$\Delta E_{th} = 3 n R \Delta T$$

Question 16

During an isothermal expansion of an ideal gas, which of the following is true?

Accepted Answer

The temperature remains constant and $$pV is $$constant.

Question 17

A $$0.016$$ mol sample of helium expands from $$1.0 	imes 10$$^{-3}$$ m^3$ at 4.0$$ 	imes $$10^5 Pa to$$ $$3.0 	imes 10$$^{-3}$$ m^3$ at 2.0$$ 	imes $$10^5 Pa. $$What is the total heat $$Q$$ added to the gas? ($$R = 8.31 J/$$mol K)

Accepted Answer

$$90 J$$

Question 18

Which of the following best describes thermal equilibrium?

Accepted Answer

Two systems are at the same temperature and no net heat energy is transferred.

Question 19

If the temperature of an ideal gas is quadrupled, by what factor does the root-mean-square speed of its molecules change?

Accepted Answer

It doubles.

Thermal Properties of Matter: Atomic Model, Ideal Gases, and Thermal Expansion lecture 20

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