Question 1

A gas is compressed from an initial volume of 5.55 L to a final volume of 0.700 L by an external pressure of 1.00 atm. During the compression, the gas releases $$|224.0| J of $$heat. What is the change in internal energy ($$\Delta U) of $$the gas? (Use $$1\ \mathrm{L\cdot atm} = 101.3\ \mathrm{J})$$

Accepted Answer

$$\Delta U = 663\ \mathrm{J}$$

Question 2

A 25.0-L sample of gas is compressed by a constant pressure of $$1.267 	imes 10^5$ Pa. If 328 J of work was done on the gas, what will be the final volume of the gas? (Given: 1$$\ \mathrm{L\cdot atm} = 101.3\ \mathrm{J}$$, 101$$\ \mathrm{kPa} = 1\ \mathrm{atm}$$)

Accepted Answer

Final volume = $$21.7\ \mathrm{L}$$

Question 3

A 0.250-L sample of $$0.400\ \mathrm{M}\ \mathrm{Pb(NO_3$)_2} is $$added to 0.500 L of $$0.400\ \mathrm{M}\ \mathrm{Na_2SO_4} in a $$calorimeter with a total heat capacity of $$388\ \mathrm{J\cdot K$$^{-1}$$} at $$constant pressure. The temperature change is $$+3.22\ ^\circ\mathrm{C}. $$Calculate $$\Delta H^\circ_{\mathrm{rxn}}$$ for the reaction: $$\mathrm{Na_2SO_4(aq) + Pb(NO_3$)_2(aq) \rightarrow $$PbSO_4$$(s) + 2 $$NaNO_3$$(aq)}.$$

Accepted Answer

$$\Delta H^\circ_{\mathrm{rxn}} = -12.5\ \mathrm{kJ\cdot $$mol^{-1}$$}$$

Question 4

A calorimeter contains 80.0 grams of water at $$20.00\ ^\circ\mathrm{C}. $$Calculate the expected final temperature when 26.4 grams of an insoluble material at $$98.56\ ^\circ\mathrm{C} is $$added. The specific heat of the material is $$0.331\ \mathrm{J\cdot g$$^{-1}$$\cdot ^\circ C$$^{-1}$$}$$ and that of water is $$4.184\ \mathrm{J\cdot g$$^{-1}$$\cdot ^\circ C$$^{-1}$$}.$$

Accepted Answer

Final temperature = $$22.0\ ^\circ\mathrm{C}$$

Question 5

A typical small candy contains 10 nutritional Calories of energy. ($$1\ \mathrm{Calorie} = 1000\ \mathrm{calories}$$, $$1\ \mathrm{calorie} = 4.184\ \mathrm{J}). $$How many candies must be burned in a bomb calorimeter with a total heat capacity of $$29.8\ \mathrm{kJ\cdot K$$^{-1}$$} to $$raise the temperature by $$8.4\ ^\circ\mathrm{C}$$?

Accepted Answer

6 candies

Question 6

Calculate the standard enthalpy of reaction for $$2\ \mathrm{C(graphite)} + 3\ \mathrm{H_2$(g)} \rightarrow \mathrm{C_2H_6(g)}$$ given the following data: $$\Delta H^\circ_{\mathrm{comb}}(\mathrm{C(graphite)}) = -393.5\ \mathrm{kJ\cdot $$mol^{-1}$$}$$, $$\Delta H^\circ_{\mathrm{rxn}}(\mathrm{H_2$(g) + 1/2 O_2$(g) \rightarrow H_2O(l)}) = -285.8\ \mathrm{kJ\cdot $$mol^{-1}$$}$$, $$\Delta H^\circ_{\mathrm{rxn}}(2\mathrm{C_2H_6(g)} + 7\mathrm{O_2$(g)} \rightarrow 4\mathrm{CO_2$(g)} + 6\mathrm{H_2O(l)}) = -3119.6\ \mathrm{kJ\cdot $$mol^{-1}$$}.$$

Accepted Answer

$$\Delta H^\circ_{\mathrm{rxn}} = -84.6\ \mathrm{kJ\cdot $$mol^{-1}$$}$$

Question 7

Estimate the heat of reaction at 298 K for $$\mathrm{Br_2$(g) + 3F_2(g) \rightarrow 2BrF_3(g)}$$ using the following bond enthalpies: $$(\mathrm{Br-Br}) = 192\ \mathrm{kJ\cdot $$mol^{-1}$$}$$, $$(\mathrm{F-F}) = 158\ \mathrm{kJ\cdot $$mol^{-1}$$}$$, $$(\mathrm{Br-F}) = 197\ \mathrm{kJ\cdot $$mol^{-1}$$}.$$

Accepted Answer

$$\Delta H = -516\ \mathrm{kJ}$$

Question 8

Which of the following processes is driven primarily by an increase in entropy (not enthalpy)?

Accepted Answer

Boiling of water

Question 9

When $$\mathrm{NH_4NO_3} is $$dissolved in $$25^\circC $$water, the solution becomes colder. What does this indicate about the solubility of $$\mathrm{NH_4NO_3} if $$the temperature is lowered?

Accepted Answer

The solubility of $$\mathrm{NH_4NO_3}$$ will decrease

Question 10

How many of the following have a standard enthalpy of formation ($$\Delta H^\circ_f) of $$zero? $$\mathrm{Br_2$(g)}$$, $$\mathrm{Hg(l)}$$, $$\mathrm{Mo(l)}$$, $$\mathrm{F_2$(g)}$$, $$\mathrm{I_2$(g)}$$, $$\mathrm{H(g)}$$, $$\mathrm{Mg(s)}$$

Accepted Answer

3

Question 11

Which statement is always true of the internal energy of a system and its surroundings during an energy exchange with an endothermic value of $$\Delta U_{system}$$?

Accepted Answer

The internal energy of the system increases while the internal energy of the surroundings decreases.

Question 12

If the standard enthalpy of combustion of $$\mathrm{CH_3COOH(l)} at 298 K is$$ $$-875\ \mathrm{kJ\cdot $$mol^{-1}$$}$$, estimate the standard enthalpy of formation of $$\mathrm{CH_3COOH(l)} in$$ $$\mathrm{kJ\cdot $$mol^{-1}$$}. $$Given: $$\Delta H^\circ_f(\mathrm{CO_2$(g)}) = -394\ \mathrm{kJ\cdot $$mol^{-1}$$}$$, $$\Delta H^\circ_f(\mathrm{H_2O(l)}) = -286\ \mathrm{kJ\cdot $$mol^{-1}$$}.$$

Accepted Answer

$$\Delta H^\circ_f = -480$$

Question 13

Which of the following would you expect to have both a decrease in solubility in water with increasing temperature and a negative entropy of solution ($$\Delta S_{sol} \u003c 0$$)?

Accepted Answer

Only $$\mathrm{N_2$}$$

Question 14

How many of the following isothermal reactions have a positive change in entropy? $$\mathrm{$$SiO_2$$(s) + 4HF(g) \rightarrow $$SiF_4$$(g) + 2H_2O(g)}$$; mixing alcohol and water; sublimation of $$\mathrm{CO_2$}$$; $$\mathrm{O_2$(g)}$$ dissolving in ethanol; $$\mathrm{H_2$(g) + 1/2O_2(g) \rightarrow H_2O(g)}$$; condensation of water.

Accepted Answer

4

Question 15

A substance requires 6.0 Joules of energy to heat 10.0 grams of the material by $$2.4\ ^\circ\mathrm{C}. $$What is its specific heat capacity?

Accepted Answer

$$0.24\ \mathrm{J\cdot g$$^{-1}$$\cdot ^\circ C$$^{-1}$$}$$

Question 16

Which of the following statements is true of the internal energy of a system and its surroundings during an energy exchange with a positive value of $$\Delta U_{system}$$?

Accepted Answer

The internal energy of the system increases while the energy of the surroundings decreases.

Question 17

For how many of the following does the entropy decrease: mixing sugar into tea, condensation of a gas, dissolving of $$\mathrm{O_2$(g)}$$ into $$\mathrm{H_2O(l)}$$, shuffling a deck of cards, $$\mathrm{C(s) + 1/2 O_2$(g) \rightarrow CO(g)}$$, sublimation of $$\mathrm{CO_2$(s)}$$?

Accepted Answer

3

Question 18

When $$\mathrm{$$MnSO_4$$} is $$dissolved in $$25^\circC $$water, the solution becomes hotter. What does this indicate about the solubility of $$\mathrm{$$MnSO_4$$} if $$the temperature is raised?

Accepted Answer

The solubility of $$\mathrm{$$MnSO_4$$}$$ will decrease

Question 19

Use average molar bond energies to estimate $$\Delta H^\circ_{\mathrm{rxn}}$$ for $$2\mathrm{CH_3CH_2OH(g)} + 2\mathrm{Cl_2$(g)} \rightarrow 2\mathrm{CH_3CH_2OCl(g)} + 2\mathrm{HCl(g)}$$ given: $$(\mathrm{O-Cl}) = 269\ \mathrm{kJ\cdot $$mol^{-1}$$}$$, $$(\mathrm{O-H}) = 464\ \mathrm{kJ\cdot $$mol^{-1}$$}$$, $$(\mathrm{C-O}) = 351\ \mathrm{kJ\cdot $$mol^{-1}$$}$$, $$(\mathrm{C=O}) = 730\ \mathrm{kJ\cdot $$mol^{-1}$$}$$, $$(\mathrm{C-C}) = 347\ \mathrm{kJ\cdot $$mol^{-1}$$}$$, $$(\mathrm{C=C}) = 615\ \mathrm{kJ\cdot $$mol^{-1}$$}$$, $$(\mathrm{C-H}) = 414\ \mathrm{kJ\cdot $$mol^{-1}$$}$$, $$(\mathrm{H-Cl}) = 431\ \mathrm{kJ\cdot $$mol^{-1}$$}$$, $$(\mathrm{Cl-Cl}) = 243\ \mathrm{kJ\cdot $$mol^{-1}$$}.$$

Accepted Answer

$$\Delta H^\circ_{\mathrm{rxn}} = 14\ \mathrm{kJ\cdot $$mol^{-1}$$}$$

Practice Test 2-1: Thermodynamics, Calorimetry, and Entropy Guidance

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