Q: A gas has a volume of 43.0 L at 18°C and a pressure of 765 torr. If the volume changes to 26.0 L and the temperature changes to 86°C, what is the new pressure (in torr) if the amount of gas stays the same? Use three significant figures.

6.04\times $$10^{3}$$ \text{ torr}

Q: A fluorescent tube light with a length of 4.00 ft and a diameter of 1.5 inches contains mercury vapor and argon. A specific fluorescent bulb contains 0.263% mercury and has a total pressure inside the lamp of 304 Pa. How many argon atoms are present in the lamp? State all assumptions.

2.69\times $$10^{19}$$ \text{ atoms}

Q: A 135 mL sample of butane gas is collected over water at a temperature of 28°C and pressure of 742 torr. Calculate the number of moles of butane in the collected sample.

5.13\times $$10^{-3}$$ \text{ mol}

Q: What would be the density of oxygen, O$$_2$$, at each condition? (a) STP (b) 1.56 atm and 66.0°C. Answer in grams per liter.

a) 1.43 \text{ g/L}; b) 1.79 \text{ g/L}

Q: Determine the pressure exerted by a 1.50 mol sample of NH$$_3$$ gas at 60.0°C that occupies a volume of 56.8 L considering that (a) it behaves as an ideal gas (b) it behaves as a real gas (using the van der Waals equation: $$a = 4.17\ \text{L}^2\text{atm}/\text{mol}^2$$, $$b = 0.0371\ \text{L}/\text{mol}).$$

(a) P = 0.722 \text{ atm}; (b) P = 0.612 \text{ atm}

Question 1

A gas has a volume of 43.0 L at 18°C and a pressure of 765 torr. If the volume changes to 26.0 L and the temperature changes to 86°C, what is the new pressure (in torr) if the amount of gas stays the same? Use three significant figures.

Accepted Answer

6.04	imes $$10^{3}$$ 	ext{ torr}

Question 2

A vessel contains CO, H$$_2$$, and O$$_2. $$The mole fractions of H$$_2$$ and O$$_2$$ are 0.17 and 0.62, respectively. What is the mole fraction of CO?

Accepted Answer

0.21

Question 3

A fluorescent tube light with a length of 4.00 ft and a diameter of 1.5 inches contains mercury vapor and argon. A specific fluorescent bulb contains 0.263% mercury and has a total pressure inside the lamp of 304 Pa. How many argon atoms are present in the lamp? State all assumptions.

Accepted Answer

2.69	imes $$10^{19}$$ 	ext{ atoms}

Question 4

Calculate the molar mass of the unknown liquid using the Dumas method: mass of vapor = 1.3214 g, volume of flask = 500 mL, pressure = 754.3 Torr, temperature = 99.43°C.

Accepted Answer

76.95 	ext{ g/mol}

Question 5

A sample of phosgene gas (COCl$$_2) is $$kept at 850 torr and 35.0°C. Determine its density in g/L.

Accepted Answer

3.15 	ext{ g/L}

Question 6

A 135 mL sample of butane gas is collected over water at a temperature of 28°C and pressure of 742 torr. Calculate the number of moles of butane in the collected sample.

Accepted Answer

5.13	imes $$10^{-3}$$ 	ext{ mol}

Question 7

What would be the density of oxygen, O$$_2$$, at each condition? (a) STP (b) 1.56 atm and 66.0°C. Answer in grams per liter.

Accepted Answer

a) 1.43 	ext{ g/L}; b) 1.79 	ext{ g/L}

Question 8

A Kr gas was allowed to effuse through a small hole under constant pressure. The 2 L sample of Kr took 96.0 s to effuse. Another gas of unknown identity went through the same conditions. It took a 2 L sample of the unknown gas 55.5 s to effuse. Calculate the molar mass of the unknown gas.

Accepted Answer

20.2 	ext{ g/mol}

Question 9

Explain how the following changes affect the $$v_{	ext{rms}} of a $$gas: (a) increasing pressure, (b) decreasing volume, (c) decreasing temperature.

Accepted Answer

(a) no effect; (b) no effect; (c) decrease

Question 10

At STP, consider the three separate 10-L samples of He, O$$_2$$, and Cl$$_2$$ behaving ideally. Rank them in order of increasing average kinetic energy and increasing average velocity.

Accepted Answer

He \u003c $$O_2$$ \u003c $$Cl_2$$; All gases will have the same average kinetic energy

Question 11

Which of the following statements is true for the image shown where gas A and B are different gases? (Graph shows molecular velocity distributions for A and B.)

Accepted Answer

The root-mean-square speed is the highest speed for both gas A and B.

Question 12

Identify which molecule has the higher molar mass and which has the higher rate of effusion based on the molecular velocity distribution shown below. (Molecule X = blue, Molecule Y = yellow)

Accepted Answer

Higher MM: Y, Higher rate of effusion: X

Question 13

Two containers with a volume of 150 L are filled with gas at 350 K. One container holds 5 moles of Ar, while another holds 5 moles of CO. Based on kinetic molecular theory, which gas has a faster average speed?

Accepted Answer

CO has a faster average speed than Ar.

Question 14

Determine the pressure exerted by a 1.50 mol sample of NH$$_3$$ gas at 60.0°C that occupies a volume of 56.8 L considering that (a) it behaves as an ideal gas (b) it behaves as a real gas (using the van der Waals equation: $$a = 4.17\ 	ext{L}^2	ext{atm}/	ext{mol}^2$$, $$b = 0.0371\ 	ext{L}/	ext{mol}).$$

Accepted Answer

(a) P = 0.722 	ext{ atm}; (b) P = 0.612 	ext{ atm}

Question 15

On average, a television consumes 107 kWh of electricity per year. Calculate the kilojoules of electricity consumed in three years.

Accepted Answer

5.39 	imes $$10^{5}$$ 	ext{ kJ}

Question 16

Determine the potential energy of a 48 kg swimmer at the apex of his dive from an 8.0 m platform if the apex of the dive is 8.6 m relative to the surface of the water.

Accepted Answer

4.0 	imes $$10^{3}$$ 	ext{ J}

Question 17

Which of the following statements is true based on the first law of thermodynamics?

Accepted Answer

Energy is conserved.

Question 18

The internal energy ($$\Delta E) $$and the enthalpy change ($$\Delta H) $$are the same for a reaction and both are measured at constant pressure. Is this statement true or false?

Accepted Answer

False

Question 19

Why do the surroundings feel colder during an endothermic reaction?

Accepted Answer

The reaction absorbs heat from the surroundings.

Question 20

Suppose that 0.130 kg of a substance is initially at 25.0°C. What is the final temperature of the substance upon absorbing 2.35 kJ of heat if its specific heat capacity is 0.456 J/g°C?

Accepted Answer

64.6 	ext{ °C}

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