Q: A gas is confined to a cylinder under constant pressure of 2.0 atm. When the gas undergoes a chemical reaction, it absorbs 824 J of heat and the volume changes from 6.20 L to 3.00 L. What is the value of work ($$w) $$done during this process?

$$w = -2.0\ \text{atm} \times (6.20\ \text{L} - 3.00\ \text{L})$$

Question 1

A sample of carbon dioxide weighing 44.0 g occupies 32.68 L at 65°C and 645 torr. What is its volume at STP (0°C, 1 atm)?

Accepted Answer

35.2 L

Question 2

Which equation best represents the first law of thermodynamics (conservation of energy)?

Accepted Answer

$$\Delta E_{system} = -\Delta E_{surrounding}$$

Question 3

According to the kinetic-molecular theory, why does the pressure of a gas increase as its temperature increases?

Accepted Answer

Both the gas molecules collide more frequently with the wall and the gas molecules collide more energetically with the wall.

Question 4

If 16.7 kJ of energy is absorbed by a 225-g sample of benzene at 20.0°C, what is its final temperature? (Specific heat $$c = 1.74\ 	ext{J}\ 	ext{g}^{-1}\ ^\circ	ext{C}^{-1})$$

Accepted Answer

36.7°C

Question 5

A balloon full of hydrogen is lowered to the bottom of a lake that is 10 m deep. If the temperature of the gas does not change, what happens to the density of the gas?

Accepted Answer

Density of hydrogen will increase

Question 6

Which law states that the pressure of an ideal gas is inversely proportional to its volume at constant temperature and number of moles?

Accepted Answer

Boyle's Law

Question 7

Which of the following gases has a density of 1.2 g/L in a vessel of 3.0 L, at 0.78 atm and 25°C?

Accepted Answer

Cl$$_2$$

Question 8

Which of the following is a correct formation reaction?

Accepted Answer

C (graphite) + 4 H (g) → CH$$_4 (g)$$

Question 9

A gas mixture of N$$_2$$ and CO$$_2$$ has a total pressure of 8.00 atm and contains 12.5 mol of gas. If the partial pressure of N$$_2 is 3.69 $$atm, how many moles of CO$$_2$$ are present?

Accepted Answer

8.81 mol

Question 10

When 15.3 g of sodium nitrate is dissolved in water in a bomb calorimeter, the temperature falls from 25.00°C to 21.56°C. If the heat capacity of the solution and calorimeter is 1071 J/°C, what is the enthalpy change for the process when 1 mol of sodium nitrate dissolves in water?

Accepted Answer

$$-2410\ 	ext{J/mol}$$

Question 11

Calculate the $$\Delta H^\circ_{rxn}$$ for the following reaction: H$$_3$$AsO$$_4(aq) + 4H$_2(g$$) → AsH$$_3(g) + 4H$_2O(l). $$Given: $$\Delta H^\circ_f$$ [AsH$$_3(g$$)] = 66.4 kJ/mol; $$\Delta H^\circ_f$$ [H$$_3$$AsO$$_4(aq$$)] = -904.6 kJ/mol; $$\Delta H^\circ_f$$ [H$$_2O(l$$)] = -285.8 kJ/mol.

Accepted Answer

$$+1872.4\ 	ext{kJ}$$

Question 12

Which gaseous element diffuses 3.98 times as fast as O$$_2$$?

Accepted Answer

He

Question 13

A gas is confined to a cylinder under constant pressure of 2.0 atm. When the gas undergoes a chemical reaction, it absorbs 824 J of heat and the volume changes from 6.20 L to 3.00 L. What is the value of work ($$w) $$done during this process?

Accepted Answer

$$w = -2.0\ 	ext{atm} 	imes (6.20\ 	ext{L} - 3.00\ 	ext{L})$$

Question 14

An aerosol can contains gas under a pressure of 4.50 atm at 20.0°C. If the can is left on a hot, sandy beach and the pressure increases to 4.80 atm, what is the beach temperature in °C?

Accepted Answer

33.3°C

Question 15

Which of the following statements about the kinetic-molecular theory is FALSE?

Accepted Answer

Gas particles exert attractive forces on each other.

Question 16

A 0.4891 mol sample of N$$_2 is at 125 $$atm and 28.5°C. Which equation would you use to calculate the non-ideal volume of the gas?

Accepted Answer

$$\left( P + \frac{a n^2$}{V^2$} \right) (V - n b) = nRT$$

Question 17

Which of the following is NOT a state function?

Accepted Answer

Work ($$w)$$

Question 18

A medical oxygen tank contains O$$_2 at 5.00 $$atm and 25°C. If a patient uses 2.0 L of O$$_2 at 1.00 $$atm and 37°C, what volume of O$$_2$$ must be released from the tank to supply this amount?

Accepted Answer

0.48 L

CHEM 161 Exam 3A Study Guidance: Gas Laws, Thermodynamics, and Calorimetry

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