Q: A 3.50 L sample of methane gas at STP contains how many molecules of methane?

$$9.4 \times 10$$^{22}$$ molecules

Question 1

A sample of gas occupies 2.50 L at a pressure of 1.20 atm. If the pressure is increased to 2.40 atm at constant temperature, what will be the new volume of the gas?

Accepted Answer

$$1.25\ \mathrm{L}$$

Question 2

Which of the following best describes Boyle's Law?

Accepted Answer

At constant temperature and amount of gas, the pressure and volume of a gas are inversely proportional.

Question 3

A weather balloon is filled with 5.00 L of helium at 1.00 atm and $$25^\circ\mathrm{C}. If $$the balloon rises to a region where the pressure is 0.500 atm and the temperature is $$-25^\circ\mathrm{C}$$, what is the new volume of the balloon? (Assume ideal gas behavior.)

Accepted Answer

$$7.32\ \mathrm{L}$$

Question 4

Which equation represents the combined gas law?

Accepted Answer

$$\dfrac{P_1V_1}{T_1$} = \dfrac{P_2V_2}{T_2$}$$

Question 5

A 3.50 L sample of methane gas at STP contains how many molecules of methane?

Accepted Answer

$$9.4 	imes 10$$^{22}$$ molecules

Question 6

Which of the following statements about Avogadro's Law is correct?

Accepted Answer

At constant temperature and pressure, the volume of a gas is directly proportional to the number of moles.

Question 7

A 14.0 L tank contains oxygen gas at 395 torr and $$37.0^\circ\mathrm{C}. $$What mass of $$\mathrm{O}_2 is in $$the tank? ($$R = 62.364\ \mathrm{L\cdot torr\cdot $$mol^{-1}$$\cdot K$$^{-1}$$}$$; molar mass $$\mathrm{O}_2 = 32.00\ \mathrm{g/mol})$$

Accepted Answer

$$7.10\ \mathrm{g}$$

Question 8

Which of the following is NOT a diatomic gas under standard conditions?

Accepted Answer

$$\mathrm{CO}_2$$

Question 9

A mixture of gases contains 73 mm Hg of He, 835 mm Hg of Ar, and 111 mm Hg of Xe. What is the total pressure of the mixture?

Accepted Answer

$$1355\ \mathrm{mm\ Hg}$$

Question 10

Which of the following is the correct value and units for the gas constant $$R$$ when pressure is in atm and volume is in liters?

Accepted Answer

$$0.0821\ \mathrm{L\cdot atm\cdot $$mol^{-1}$$\cdot K$$^{-1}$$}$$

Question 11

A gas sample has a pressure of 760 mm Hg, a volume of 233 L, and a temperature of $$22^\circ\mathrm{C}. If $$the temperature is lowered to $$-54^\circ\mathrm{C}$$ and the pressure is changed to 511 mm Hg, what is the new volume?

Accepted Answer

$$257\ \mathrm{L}$$

Question 12

Which of the following best explains why the pressure of a gas increases when its volume decreases at constant temperature?

Accepted Answer

The gas molecules collide with the walls more frequently due to reduced space.

Question 13

Which law is used to calculate the volume of a gas at a new temperature, assuming constant pressure and amount of gas?

Accepted Answer

Charles's Law

Question 14

A 0.150 atm sample of gas occupies 35.0 L. If the pressure is increased to 0.750 atm at constant temperature, what is the new volume?

Accepted Answer

$$7.00\ \mathrm{L}$$

Question 15

Which of the following is the correct form of the ideal gas law?

Accepted Answer

$$PV = nRT$$

Question 16

If the temperature of a fixed amount of gas is doubled (in Kelvin) at constant pressure, what happens to the volume?

Accepted Answer

The volume doubles.

Question 17

Which of the following is a correct statement of Charles's Law?

Accepted Answer

At constant pressure and amount of gas, the volume of a gas is directly proportional to its Kelvin temperature.

Question 18

A sample of gas has a volume of 10.0 L at 300 K. If the temperature is increased to 600 K at constant pressure, what is the new volume?

Accepted Answer

$$20.0\ \mathrm{L}$$

Question 19

Which of the following is a correct rearrangement of the ideal gas law to solve for the number of moles, $$n$$?

Accepted Answer

$$n = \dfrac{PV}{RT}$$

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