Q: At standard temperature and pressure (STP), what is the molar volume of an ideal gas?

$$ 22.4 \; L \; \text{mol}^{-1} $$

Q: Which of the following is the correct formula for specific gravity of a gas?

$$ SG = \frac{\text{density of gas}}{\text{density of air (reference gas)}} $$

Question 1

Which of the following best describes the difference between a gas and a vapor?

Accepted Answer

A vapor is the gaseous form of a substance that is liquid or solid under standard conditions, while a gas is the gaseous form under standard conditions.

Question 2

Which equation represents Boyle's Law?

Accepted Answer

$$ P_1$ V_1$ = P_2$ V_2$ $$

Question 3

A sample of nitrogen gas occupies 10 L at 2 atm and 300 K. What will be its volume at 1 atm and 300 K?

Accepted Answer

20 L

Question 4

Which of the following is the correct form of the Ideal Gas Law?

Accepted Answer

$$ PV = nRT $$

Question 5

At standard temperature and pressure (STP), what is the molar volume of an ideal gas?

Accepted Answer

$$ 22.4 \; L \; 	ext{mol}^{-1} $$

Question 6

A tank contains $$ N_2$  at 8 $$atm and 33°C. When 2.2 kg of the gas is removed, the pressure goes down to 7 atm and the temperature to 28°C. What is the volume of the tank? (Molar mass of $$ N_2$  = 28 g/$$mol)

Accepted Answer

$$ 56.6 \; L $$

Question 7

Which of the following is the correct expression for the density of a gas using the Ideal Gas Law?

Accepted Answer

$$ \rho = \frac{PM}{RT} $$

Question 8

A cylinder contains butane gas at 120 psig and 27°C. After some is used, the pressure drops to 55 psig at the same temperature. What fraction of the butane was used?

Accepted Answer

$$ \frac{120 - 55}{120} = 0.54 $$

Question 9

Which of the following is the correct formula for specific gravity of a gas?

Accepted Answer

$$ SG = \frac{	ext{density of gas}}{	ext{density of air (reference gas)}} $$

Question 10

Which of the following statements about vapor is TRUE?

Accepted Answer

Vapor is the gaseous form of a substance that is liquid or solid under standard conditions.

Question 11

The combined gas law is useful because it:

Accepted Answer

Eliminates the need for the gas constant $$ R $$ and minimizes unit conversions.

Question 12

If the pressure of a gas is measured as 120 psig, what is its absolute pressure in psi? (Atmospheric pressure = 14.7 psi)

Accepted Answer

$$ 134.7 \; psi $$

Question 13

Which of the following equations is used to relate the volume of a gas at non-standard conditions to its volume at STP?

Accepted Answer

$$ \frac{P_G V_G}{T_G} = n V_m \frac{P_S}{T_S} $$

Question 14

A chemical reaction produces acetylene gas ($$ C_2H_2 ) $$from calcium carbide and water. If 3.5 kg of calcium carbide is used, how many moles of acetylene are produced? (Molar mass of $$ $$CaC_2$$  = 64 g/$$mol)

Accepted Answer

54.7 mol

Question 15

Which of the following is NOT a property of gases under standard conditions?

Accepted Answer

High density

Question 16

A gas sample at 1 atm and 273 K occupies 22.4 L. If the temperature is increased to 546 K at constant pressure, what is the new volume?

Accepted Answer

44.8 L

Question 17

Which of the following statements about the Ideal Gas Law is correct?

Accepted Answer

It assumes no intermolecular forces and that the volume of gas molecules is negligible.

Question 18

Which gas law would you use to determine the change in pressure when the temperature and volume of a gas are both changed?

Accepted Answer

Combined Gas Law

Question 19

A gas lamp burns 0.08 $$ m^3$  of $$acetylene per hour at 26°C and 745 torr. How many moles of acetylene are consumed per hour? ($$ R = 0.08206 \; L \; atm \; $$mol^{-1}$$ \; K$$^{-1}$$ $$; 1 atm = 760 torr)

Accepted Answer

3.18 mol

Gases and Vapors: Properties, Laws, and Calculations

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