Question 1

Which of the following best describes an isolated system in thermodynamics?

Accepted Answer

A system that cannot exchange either mass or energy with its surroundings.

Question 2

Given the equation $$\Delta E = E_{	ext{final}} - E_{	ext{initial}}$$, what does a negative $$\Delta E$$ indicate about the system?

Accepted Answer

The system released energy to the surroundings.

Question 3

A chemical reaction occurs in a cylinder fitted with a piston. The system loses 1150 J of heat and the surroundings do 480 J of work on the system. What is the change in internal energy ($$\Delta E) of $$the system?

Accepted Answer

$$\Delta E = -670 	ext{ J}$$

Question 4

Which of the following is a state function?

Accepted Answer

Internal energy ($$E)$$

Question 5

At constant pressure, which equation correctly relates the change in enthalpy ($$\Delta H) to $$the heat exchanged?

Accepted Answer

$$\Delta H = q$$

Question 6

A piston expands from 0.250 L to 0.980 L against a constant pressure of 1.35 atm. How much work (in J) is done by the system? ($$1 	ext{ L} \cdot 	ext{atm} = 101.3 	ext{ J})$$

Accepted Answer

$$-99.8 	ext{ J}$$

Question 7

Which statement is true about exothermic reactions?

Accepted Answer

They release heat to the surroundings and have $$\Delta H \u003c 0.$$

Question 8

The enthalpy change for a reaction is equal in magnitude but opposite in sign to the enthalpy change for the reverse reaction. Which property does this illustrate?

Accepted Answer

Enthalpy is an extensive property.

Question 9

A student mixes 50 mL of 1.0 M HCl and 50 mL of 1.0 M NaOH in a coffee-cup calorimeter. The temperature increases from 21.0°C to 27.5°C. Assuming the density is 1.0 g/mL and specific heat is 4.18 J/g-K, what is the enthalpy change per mole of HCl?

Accepted Answer

$$-54 	ext{ kJ/mol}$$

Question 10

Which equation correctly expresses the work done by a gas during expansion at constant pressure?

Accepted Answer

$$w = -P\Delta V$$

Question 11

If a process is endothermic, which of the following is true?

Accepted Answer

$$\Delta H \u003e 0$$

Question 12

Which of the following best describes the specific heat capacity ($$C_s) of a $$substance?

Accepted Answer

The amount of energy required to raise the temperature of one gram of substance by 1 K.

Question 13

In a bomb calorimeter, which quantity is most directly measured?

Accepted Answer

Change in internal energy ($$\Delta E)$$

Question 14

A 4.00 g sample of methylhydrazine ($$\mathrm{CH_3N_2H_3}) is $$combusted in a bomb calorimeter with a heat capacity of 7.79 kJ/K. The temperature rises from 25.00°C to 39.50°C. What is the total heat released by the reaction?

Accepted Answer

$$113 	ext{ kJ}$$

Question 15

Which of the following is NOT true about state functions?

Accepted Answer

Heat ($$q) $$and work ($$w) $$are state functions.

Question 16

Which formula is used to calculate the heat required to raise the temperature of a sample?

Accepted Answer

$$q = mC_s\Delta T$$

Question 17

Why is the enthalpy change for a reaction dependent on the physical states of reactants and products?

Accepted Answer

Because different states have different internal energies.

Question 18

Which of the following is the correct definition of enthalpy ($$H$$)?

Accepted Answer

$$H = E + PV$$

Question 19

A reaction is carried out in a coffee-cup calorimeter. Which assumption is most important for accurate measurement of $$\Delta H$$?

Accepted Answer

The calorimeter loses only a negligible quantity of heat.

Thermochemistry: Energy, Internal Energy, and Thermodynamic Systems

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