Q: Calculate the heat required to raise the temperature of 1000 g of water from $$21.0\ ^\circ \mathrm{C} to$$ $$37.0\ ^\circ \mathrm{C}$$, given the specific heat capacity of water is $$4.18\ \mathrm{J}\ \mathrm{g}^{-1}\ ^\circ \mathrm{C}^{-1}.$$

$$6.69 \times 10^4$\ \mathrm{J}$$

Q: A gas expands against a constant external pressure. Which formula is used to calculate the work done by the system?

$$w = -P_{\text{ext}} \Delta V$$

Q: Using Hess’s Law, which equation is used to calculate the standard enthalpy change of a reaction?

$$\Delta H^\circ = \sum \nu \Delta H_f^\circ \text{(products)} - \sum \nu \Delta H_f^\circ \text{(reactants)}$$

Q: A sample of 50.0 g of water is heated from $$22.0\ ^\circ \mathrm{C} to$$ $$28.8\ ^\circ \mathrm{C}. $$How much heat is absorbed? (Specific heat capacity of water is $$4.18\ \mathrm{J}\ \mathrm{g}^{-1}\ ^\circ \mathrm{C}^{-1})$$

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

Question 1

Which of the following best describes an isolated system, as shown in the provided diagrams?

Accepted Answer

A system that does not exchange either matter or energy with its surroundings.

Question 2

A coffee-cup calorimeter is used to measure the heat of a reaction. Which type of system does it most closely represent?

Accepted Answer

Closed system

Question 3

Calculate the heat required to raise the temperature of 1000 g of water from $$21.0\ ^\circ \mathrm{C} to$$ $$37.0\ ^\circ \mathrm{C}$$, given the specific heat capacity of water is $$4.18\ \mathrm{J}\ \mathrm{g}^{-1}\ ^\circ \mathrm{C}^{-1}.$$

Accepted Answer

$$6.69 	imes 10^4$\ \mathrm{J}$$

Question 4

In a bomb calorimeter experiment, the temperature of the water increases from $$24.92\ ^\circ \mathrm{C} to$$ $$28.33\ ^\circ \mathrm{C}. If $$the heat capacity of the calorimeter is $$4.81\ \mathrm{kJ}/^\circ \mathrm{C}$$, what is the total heat absorbed?

Accepted Answer

$$16.4\ \mathrm{kJ}$$

Question 5

Which equation correctly relates the change in internal energy ($$\Delta U$$), heat ($$q$$), and work ($$w) $$for a system?

Accepted Answer

$$\Delta U = q + w$$

Question 6

A gas expands against a constant external pressure. Which formula is used to calculate the work done by the system?

Accepted Answer

$$w = -P_{	ext{ext}} \Delta V$$

Question 7

Which of the following is a state function?

Accepted Answer

Internal energy ($$U)$$

Question 8

If a reaction occurs at constant volume, which expression is correct for the change in internal energy?

Accepted Answer

$$\Delta U = q_{	ext{rxn}}$$

Question 9

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

Accepted Answer

It is zero for any element in its reference form.

Question 10

Using Hess’s Law, which equation is used to calculate the standard enthalpy change of a reaction?

Accepted Answer

$$\Delta H^\circ = \sum 
u \Delta H_f^\circ 	ext{(products)} - \sum 
u \Delta H_f^\circ 	ext{(reactants)}$$

Question 11

Which of the following best describes an exothermic reaction?

Accepted Answer

The enthalpy of the reactants is higher than that of the products.

Question 12

A sample of 50.0 g of water is heated from $$22.0\ ^\circ \mathrm{C} to$$ $$28.8\ ^\circ \mathrm{C}. $$How much heat is absorbed? (Specific heat capacity of water is $$4.18\ \mathrm{J}\ \mathrm{g}^{-1}\ ^\circ \mathrm{C}^{-1})$$

Accepted Answer

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

Question 13

Which of the following is NOT a form of kinetic energy in molecules?

Accepted Answer

Electrostatic (intermolecular attractions)

Question 14

In a calorimetry experiment, 150.0 g of lead at $$100.0\ ^\circ \mathrm{C} is $$added to 50.0 g of water at $$22.0\ ^\circ \mathrm{C}. $$The final temperature is $$28.8\ ^\circ \mathrm{C}. $$What is the specific heat capacity of lead?

Accepted Answer

$$0.13\ \mathrm{J}\ \mathrm{g}^{-1}\ ^\circ \mathrm{C}^{-1}$$

Question 15

Which of the following statements about the law of conservation of energy is correct?

Accepted Answer

The total energy of a system and its surroundings remains constant.

Question 16

A reaction occurs at constant pressure and produces a gas. Which equation relates the enthalpy change ($$\Delta H) to $$the internal energy change ($$\Delta U$$)?

Accepted Answer

$$\Delta H = \Delta U + \Delta n_{	ext{gas}}RT$$

Question 17

Which of the following is an example of an extensive property?

Accepted Answer

Enthalpy

Question 18

A chemical reaction in a bomb calorimeter causes the temperature of the water to increase. What does this indicate about the reaction?

Accepted Answer

The reaction is exothermic.

Question 19

Which equation would you use to calculate the heat required to change the temperature of a substance?

Accepted Answer

$$q = m c_p \Delta T$$

Thermochemistry: Energy, Heat, and Enthalpy in Chemical Systems

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