Q: Which equation correctly relates the heat ($$q) $$absorbed or released by a substance to its mass ($$m$$), specific heat ($$s$$), and temperature change ($$\Delta T$$)?

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

Q: A bomb calorimeter contains $$3.000\ \mathrm{kg} of $$water. Burning a sample produces $$9.598\ \mathrm{kJ} of $$heat, raising the water temperature by $$0.629\ ^\circ\mathrm{C}. If $$the specific heat of water is $$4.184\ \mathrm{J}\ \mathrm{g}^{-1}\ ^\circ\mathrm{C}^{-1}$$, what is the heat capacity of the bomb?

$$2.72 \times 10^3$\ \mathrm{J}/^\circ\mathrm{C}$$

Q: Which of the following is the correct expression for the standard enthalpy change of a reaction ($$\Delta H^\circ_{rxn}) $$using standard enthalpies of formation?

$$\Delta H^\circ_{rxn} = \sum \Delta H^\circ_f(\text{products}) - \sum \Delta H^\circ_f(\text{reactants})$$

Q: A student mixes $$100.0\ \mathrm{g} of $$water at $$22.0\ ^\circ\mathrm{C}$$ with $$50.0\ \mathrm{g} of a $$metal at $$100.0\ ^\circ\mathrm{C}. $$The final temperature is $$28.8\ ^\circ\mathrm{C}. $$What is the heat lost by the metal?

$$-1.4 \times 10^3$\ \mathrm{J}$$

Question 1

Which of the following best describes the First Law of Thermodynamics?

Accepted Answer

Energy cannot be created nor destroyed, but can be converted from one form to another.

Question 2

A 50.0 g sample of lead at $$100.0\ ^\circ\mathrm{C} is $$placed in 100.0 g of water at $$22.0\ ^\circ\mathrm{C}. $$The final temperature of the mixture is $$28.8\ ^\circ\mathrm{C}. $$What is the specific heat capacity of lead? (Specific heat of water $$= 4.184\ \mathrm{J}\ \mathrm{g}^{-1}\ ^\circ\mathrm{C}^{-1})$$

Accepted Answer

$$0.133\ \mathrm{J}\ \mathrm{g}^{-1}\ ^\circ\mathrm{C}^{-1}$$

Question 3

Which equation correctly relates the heat ($$q) $$absorbed or released by a substance to its mass ($$m$$), specific heat ($$s$$), and temperature change ($$\Delta T$$)?

Accepted Answer

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

Question 4

A bomb calorimeter contains $$3.000\ \mathrm{kg} of $$water. Burning a sample produces $$9.598\ \mathrm{kJ} of $$heat, raising the water temperature by $$0.629\ ^\circ\mathrm{C}. If $$the specific heat of water is $$4.184\ \mathrm{J}\ \mathrm{g}^{-1}\ ^\circ\mathrm{C}^{-1}$$, what is the heat capacity of the bomb?

Accepted Answer

$$2.72 	imes 10^3$\ \mathrm{J}/^\circ\mathrm{C}$$

Question 5

Which of the following reactions is exothermic?

Accepted Answer

REACTANTS $$\rightarrow$$ PRODUCTS $$+$$ ENERGY

Question 6

In a chemical reaction at constant pressure, the heat absorbed or released is called:

Accepted Answer

Enthalpy ($$H)$$

Question 7

Which of the following is the correct expression for the standard enthalpy change of a reaction ($$\Delta H^\circ_{rxn}) $$using standard enthalpies of formation?

Accepted Answer

$$\Delta H^\circ_{rxn} = \sum \Delta H^\circ_f(	ext{products}) - \sum \Delta H^\circ_f(	ext{reactants})$$

Question 8

Which statement about standard enthalpy of formation ($$\Delta H^\circ_f) is $$correct?

Accepted Answer

It is the enthalpy change when one mole of a compound is formed from its elements in their standard states at $$25\ ^\circ\mathrm{C}.$$

Question 9

Given the following reactions and their enthalpy changes:

$$\mathrm{C(graphite)} + \mathrm{O}_2(g) \rightarrow \mathrm{CO}_2(g) \quad \Delta H^\circ = -393.5\ \mathrm{kJ}$$
$$\mathrm{H}_2(g) + \frac{1}{2}\mathrm{O}_2(g) \rightarrow \mathrm{H}_2O(l) \quad \Delta H^\circ = -285.8\ \mathrm{kJ}$$
$$\mathrm{C}_2H_6(g) + \frac{7}{2}\mathrm{O}_2(g) \rightarrow 2\mathrm{CO}_2(g) + 3\mathrm{H}_2O(l)$$

Calculate $$\Delta H^\circ$$ for the combustion of ethane ($$\mathrm{C}_2H_6) $$using the direct method if $$\Delta H^\circ_f(\mathrm{C}_2H_6) = -84.7\ \mathrm{kJ}.$$

Accepted Answer

$$-1559.7\ \mathrm{kJ}$$

Question 10

Which of the following is NOT a factor that affects the amount of heat ($$q) $$required to change the temperature of a substance?

Accepted Answer

The color of the substance

Question 11

A student mixes $$100.0\ \mathrm{g} of $$water at $$22.0\ ^\circ\mathrm{C}$$ with $$50.0\ \mathrm{g} of a $$metal at $$100.0\ ^\circ\mathrm{C}. $$The final temperature is $$28.8\ ^\circ\mathrm{C}. $$What is the heat lost by the metal?

Accepted Answer

$$-1.4 	imes 10^3$\ \mathrm{J}$$

Question 12

Which of the following best describes Hess's Law?

Accepted Answer

The enthalpy change for a reaction is the same, whether it occurs in one step or several steps.

Question 13

Which of the following is the correct SI unit for energy?

Accepted Answer

$$\mathrm{Joule}\ (\mathrm{J})$$

Question 14

Which process is endothermic?

Accepted Answer

Melting of ice

Question 15

If $$1\ \mathrm{cal} = 4.184\ \mathrm{J}$$, how many joules are in $$250\ \mathrm{cal}$$?

Accepted Answer

$$1046\ \mathrm{J}$$

Question 16

Which of the following statements about enthalpy ($$H) is $$true?

Accepted Answer

Enthalpy is a state function and depends only on the initial and final states of the system.

Question 17

Which of the following is the correct formula for calculating the heat absorbed by water in a calorimeter?

Accepted Answer

$$q_{water} = m 	imes s 	imes \Delta T$$

Question 18

Which of the following is the correct definition of heat capacity ($$C$$)?

Accepted Answer

The amount of energy required to raise the temperature of a substance by $$1\ ^\circ\mathrm{C}.$$

Thermochemistry: Energy Changes in Chemical Reactions

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