Question 1

A 295 g sample of aluminum at $$3.00\ ^\circ\mathrm{C}$$ absorbs $$85.0\ \mathrm{kJ} of $$heat. If the specific heat capacity of aluminum is $$0.900\ \mathrm{J}/\mathrm{g}\ ^\circ\mathrm{C}$$, what is the final temperature of the aluminum? (Assume no heat loss to the surroundings.)

Accepted Answer

$$323\ ^\circ\mathrm{C}$$

Question 2

Which of the following best describes the sign of $$\Delta H$$ and the thermodynamic nature of the process when an ice cube melts at atmospheric pressure?

Accepted Answer

$$\Delta H \u003e 0$$, endothermic

Question 3

In the reaction $$2\ \mathrm{H}_2\mathrm{O}(g) \rightarrow 2\ \mathrm{H}_2\mathrm{O}(l)\ \Delta H = -88\ \mathrm{kJ}$$, how is heat categorized?

Accepted Answer

Product

Question 4

Given the thermochemical equation: $$\mathrm{Pb}(s) + \mathrm{PbO}_2(s) + 2\ \mathrm{SO}_3(g) \rightarrow 2\ \mathrm{PbSO}_4(s)\ \Delta H = -768\ \mathrm{kJ}$$, what is the enthalpy change when only 1 mol of $$\mathrm{PbSO}_4 is $$formed?

Accepted Answer

$$-384\ \mathrm{kJ}$$

Question 5

What is the enthalpy change (in kJ) when $$5.56\ \mathrm{g} of$$ $$\mathrm{H}_2$$ reacts according to $$2\ \mathrm{H}_2(g) + \mathrm{O}_2(g) \rightarrow 2\ \mathrm{H}_2\mathrm{O}(l)\ \Delta H = -571.66\ \mathrm{kJ}$$?

Accepted Answer

$$-787\ \mathrm{kJ}$$

Question 6

A silver block at $$58.7\ ^\circ\mathrm{C} is $$placed in $$100.0\ \mathrm{g} of $$water at $$24.9\ ^\circ\mathrm{C} in an $$insulated container. The final temperature is $$26.9\ ^\circ\mathrm{C}. If $$the specific heat capacities are $$C_{s,\mathrm{Ag}} = 0.235\ \mathrm{J}/\mathrm{g}\ ^\circ\mathrm{C}$$ and $$C_{s,\mathrm{H}_2O$$} = 4.184\ \mathrm{J}/\mathrm{g}\ ^\circ\mathrm{C}$$, what is the mass of the silver block?

Accepted Answer

$$112\ \mathrm{g}$$

Question 7

Which of the following statements is true for a chemical reaction occurring at constant volume in a bomb calorimeter?

Accepted Answer

$$q = \Delta E$$

Question 8

A balloon expands against a constant external pressure. Is the energy exchange primarily heat or work, and what is the sign of $$\Delta E$$ for the system?

Accepted Answer

Work, negative energy change

Question 9

In a constant pressure calorimeter, a student mixes $$50.0\ \mathrm{mL} of$$ $$1.0\ \mathrm{M}$$ HCl and $$50.0\ \mathrm{mL} of$$ $$1.0\ \mathrm{M}$$ NaOH$$. The temperature of the solution increases from 21.0$$\ ^\circ\mathrm{C}$$ to 27.5$$\ ^\circ\mathrm{C}$$. Assuming the solution has a density of 1.0$$\ \mathrm{g}/\mathrm{mL}$$ and a specific heat of 4.18$$\ \mathrm{J}/\mathrm{g}\ ^\circ\mathrm{C}$, what is the enthalpy change per mole of HCl?

Accepted Answer

$$-54\ \mathrm{kJ}/\mathrm{mol}$$

Question 10

Which of the following best describes an exothermic reaction?

Accepted Answer

Heat is released from the system, $$\Delta H \u003c 0$$

Question 11

For a constant volume calorimeter (bomb calorimeter), what is considered the system?

Accepted Answer

The reaction

Question 12

A $$4.00\ \mathrm{g}$$ sample of methylhydrazine ($$\mathrm{CH}_3\mathrm{NHNH}_2) is $$combusted in a bomb calorimeter. The heat capacity of the calorimeter is $$7.794\ \mathrm{kJ}/^\circ\mathrm{C}$$ and the temperature rises from $$25.00\ ^\circ\mathrm{C} to$$ $$39.50\ ^\circ\mathrm{C}. $$What is the heat of reaction per mole of methylhydrazine? (Molar mass $$= 46.1\ \mathrm{g}/\mathrm{mol})$$

Accepted Answer

$$-1,300\ \mathrm{kJ}/\mathrm{mol}$$

Question 13

What is the correct relationship for the change in internal energy ($$\Delta E) of a $$system?

Accepted Answer

$$\Delta E = q + w$$

Question 14

If $$15.53\ \mathrm{g} of$$ $$\mathrm{SO}_3$$ reacts according to $$\mathrm{Pb}(s) + \mathrm{PbO}_2(s) + 2\ \mathrm{SO}_3(g) \rightarrow 2\ \mathrm{PbSO}_4(s)\ \Delta H = -768\ \mathrm{kJ}$$, what is the enthalpy change? (Molar mass $$\mathrm{SO}_3 = 80.07\ \mathrm{g}/\mathrm{mol})$$

Accepted Answer

$$-74.5\ \mathrm{kJ}$$

Question 15

Which of the following is a state function?

Accepted Answer

Enthalpy ($$H)$$

Question 16

A chemical reaction occurs at constant pressure and releases heat to the surroundings. Which of the following statements is true?

Accepted Answer

$$\Delta H \u003c 0$$, exothermic

Question 17

Which equation correctly relates the enthalpy change ($$\Delta H) to $$the change in internal energy ($$\Delta E) at $$constant pressure?

Accepted Answer

$$\Delta H = \Delta E + P\Delta V$$

Question 18

Which of the following best describes the surroundings in a coffee-cup calorimeter experiment?

Accepted Answer

The solution (water and dissolved substances)

Thermochemistry: Heat, Work, Enthalpy, and Calorimetry

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