Q: A $$125\ \mathrm{g}$$ copper layer is heated from $$25^\circ\mathrm{C} to$$ $$300^\circ\mathrm{C}. If $$the specific heat capacity of copper is $$0.387\ \mathrm{J/g/K}$$, how much heat is required?

$$q = 1.33 \times 10^4$\ \mathrm{J}$$

Q: Given the thermochemical equation: $$2\mathrm{H_2O}(l) \rightarrow 2\mathrm{H_2$}(g) + \mathrm{O_2$}(g)\ \Delta H = 572\ \mathrm{kJ}$$, what is the enthalpy change for decomposing $$4.00$$ moles of $$\mathrm{H_2O}(l)$$?

$$1.14 \times 10^3$\ \mathrm{kJ}$$

Q: Which equation is used to calculate the heat required to change the temperature of a substance using its specific heat capacity?

$$q = m \times c \times \Delta T$$

Question 1

Which of the following best describes a state function in thermodynamics?

Accepted Answer

A property that depends only on the initial and final states of a system, not on the path taken.

Question 2

A potato cannon performs $$855\ \mathrm{J} of $$work on a potato and releases $$1422\ \mathrm{J} of $$heat. What is the change in internal energy $$(\Delta E)$$ for the burning of the fuel?

Accepted Answer

$$\Delta E = 2277\ \mathrm{J}$$

Question 3

Which equation correctly relates the change in internal energy $$(\Delta E) to $$heat $$(q)$$ and work $$(w)$$?

Accepted Answer

$$\Delta E = q + w$$

Question 4

A $$125\ \mathrm{g}$$ copper layer is heated from $$25^\circ\mathrm{C} to$$ $$300^\circ\mathrm{C}. If $$the specific heat capacity of copper is $$0.387\ \mathrm{J/g/K}$$, how much heat is required?

Accepted Answer

$$q = 1.33 	imes 10^4$\ \mathrm{J}$$

Question 5

Which of the following statements about exothermic and endothermic reactions is correct?

Accepted Answer

Exothermic reactions release heat and have $$\Delta H_{\mathrm{rxn}} \u003c 0.$$

Question 6

A $$22.05\ \mathrm{g}$$ solid is heated to $$100.00^\circ\mathrm{C}$$ and placed in $$50.00\ \mathrm{g} of $$water at $$25.10^\circ\mathrm{C}. $$The final temperature is $$28.49^\circ\mathrm{C}. $$What is the specific heat capacity of the solid? ($$c_{\mathrm{H_2O}} = 4.184\ \mathrm{J/g/}^\circ\mathrm{C})$$

Accepted Answer

$$c_{\mathrm{solid}} = 0.450\ \mathrm{J/g/}^\circ\mathrm{C}$$

Question 7

Which of the following is true about the standard enthalpy of formation $$(\Delta H_f^\circ)$$?

Accepted Answer

It is zero for any element in its standard state.

Question 8

Given the thermochemical equation: $$2\mathrm{H_2O}(l) \rightarrow 2\mathrm{H_2$}(g) + \mathrm{O_2$}(g)\ \Delta H = 572\ \mathrm{kJ}$$, what is the enthalpy change for decomposing $$4.00$$ moles of $$\mathrm{H_2O}(l)$$?

Accepted Answer

$$1.14 	imes 10^3$\ \mathrm{kJ}$$

Question 9

Which of the following best describes Hess’s Law?

Accepted Answer

The enthalpy change for a stepwise process is the sum of the enthalpy changes of the steps.

Question 10

A bomb calorimeter has a heat capacity of $$8.151\ \mathrm{kJ/K}. If $$the temperature rises from $$21.862^\circ\mathrm{C} to$$ $$26.799^\circ\mathrm{C}$$ during combustion, how much heat was released?

Accepted Answer

$$40.24\ \mathrm{kJ}$$

Question 11

Which of the following is NOT a correct statement about energy transfer?

Accepted Answer

Temperature is the same as heat.

Question 12

Which equation is used to calculate the heat required to change the temperature of a substance using its specific heat capacity?

Accepted Answer

$$q = m 	imes c 	imes \Delta T$$

Question 13

In a constant-pressure calorimetry experiment, $$0.158\ \mathrm{g} of Mg $$reacts with excess HCl in $$100.0\ \mathrm{mL} of $$solution. The temperature rises from $$25.6^\circ\mathrm{C} to$$ $$32.8^\circ\mathrm{C}. $$What is the enthalpy change per mole of Mg? ($$C_{s,\mathrm{soln}} = 4.18\ \mathrm{J/g/}^\circ\mathrm{C}$$, density $$= 1.00\ \mathrm{g/mL}$$, $$M_{\mathrm{Mg}} = 24.31\ \mathrm{g/mol})$$

Accepted Answer

$$\Delta H_{\mathrm{rxn}} = -4.6 	imes 10^5$\ \mathrm{J/mol}$$

Question 14

Which of the following is the correct formula for calculating the standard enthalpy of reaction $$(\Delta H_{\mathrm{rxn}}^\circ)$$ from standard enthalpies of formation?

Accepted Answer

$$\Delta H_{\mathrm{rxn}}^\circ = \sum m \Delta H_f^\circ(\mathrm{products}) - \sum n \Delta H_f^\circ(\mathrm{reactants})$$

Question 15

Which of the following scenarios best illustrates the concept of a system and its surroundings in thermodynamics?

Accepted Answer

A beaker of water being heated on a hot plate, where the water is the system and the air, beaker, and hot plate are the surroundings.

Question 16

If a chemical equation is reversed, what happens to the sign of $$\Delta H_{\mathrm{rxn}}$$?

Accepted Answer

It changes sign.

Question 17

Which of the following is an example of potential energy?

Accepted Answer

A compressed spring.

Question 18

Which of the following is true about the First Law of Thermodynamics?

Accepted Answer

The total energy of the universe is constant.

Thermochemistry and the First Law of Thermodynamics: Study Notes

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