Q: What is the correct formula for calculating the amount of heat transferred to a substance, given its mass ($$m$$), specific heat capacity ($$c$$), and temperature change ($$\Delta T$$)?

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

Q: In a reaction where $$\Delta n_{gas} = -3 at$$ $$298\ \mathrm{K}$$, what is the $$P-V$$ work done by the system? (Use $$R = 8.314\ \mathrm{J\ $$mol^{-1}$$\ K$$^{-1}$$})$$

$$w = -7.43 \times 10^3$\ \mathrm{J}$$

Question 1

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

Accepted Answer

Energy can neither be created nor destroyed; it can only be transferred from one object or system to another.

Question 2

A reaction in a flask releases 890 J of heat to the surroundings and performs 450 J of work on the surroundings. What is the value of $$\Delta U$$ for the system?

Accepted Answer

$$\Delta U = -1340\ \mathrm{J}$$

Question 3

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

Accepted Answer

$$\Delta U = q + w$$

Question 4

A 25.175 g pure silver coin ($$C = 0.235\ \mathrm{J\ g$$^{-1}$$\ ^\circ C$$^{-1}$$}) is $$heated from $$10.0^\circ \mathrm{C} to$$ $$37.0^\circ \mathrm{C}. $$How much heat is absorbed by the coin?

Accepted Answer

$$q = 278\ \mathrm{J}$$

Question 5

Which of the following best describes an exothermic reaction?

Accepted Answer

A reaction that releases heat to its surroundings; $$\Delta H \u003c 0.$$

Question 6

What is the correct formula for calculating the amount of heat transferred to a substance, given its mass ($$m$$), specific heat capacity ($$c$$), and temperature change ($$\Delta T$$)?

Accepted Answer

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

Question 7

A 59 g cube of aluminum ($$C = 0.903\ \mathrm{J\ g$$^{-1}$$\ ^\circ C$$^{-1}$$}) at$$ $$45.8^\circ \mathrm{C} is $$placed in $$105.39 g of $$water ($$C = 4.184\ \mathrm{J\ g$$^{-1}$$\ ^\circ C$$^{-1}$$}) at$$ $$15.4^\circ \mathrm{C}. $$Assuming no heat loss, what is the final equilibrium temperature ($$T_f$$)?

Accepted Answer

$$T_f \approx 19.6^\circ \mathrm{C}$$

Question 8

Which of the following is the correct expression for the work done by a system during a volume change at constant pressure?

Accepted Answer

$$w = -P \Delta V$$

Question 9

In a reaction where $$\Delta n_{gas} = -3 at$$ $$298\ \mathrm{K}$$, what is the $$P-V$$ work done by the system? (Use $$R = 8.314\ \mathrm{J\ $$mol^{-1}$$\ K$$^{-1}$$})$$

Accepted Answer

$$w = -7.43 	imes 10^3$\ \mathrm{J}$$

Question 10

Which statement about state functions is correct?

Accepted Answer

State functions are properties that depend only on the current state of the system, not its history.

Question 11

A bomb calorimeter contains 1.00 g of sucrose ($$C_{12}H$$_{22}$$O_{11}) $$and the temperature increases from $$24.922^\circ \mathrm{C} to$$ $$28.331^\circ \mathrm{C}. If $$the heat capacity of the calorimeter is $$4.901\ \mathrm{kJ\ ^\circ C$$^{-1}$$}$$, what is the change in internal energy ($$\Delta U$) for the reaction?

Accepted Answer

$$\Delta U = -16.71\ \mathrm{kJ}$$

Question 12

Which equation defines enthalpy ($$H) in $$terms of internal energy ($$U$$), pressure ($$P$$), and volume ($$V$$)?

Accepted Answer

$$H = U + PV$$

Question 13

Which of the following is true for the standard enthalpy of formation ($$\Delta H_f^\circ) of a $$pure element in its standard state?

Accepted Answer

$$\Delta H_f^\circ = 0$$

Question 14

Using the following standard enthalpies of formation: $$\Delta H_f^\circ(CO(g)) = -393.5 kJ/$$mol, $$\Delta H_f^\circ(C_2H_5OH(l)) = -277.6 kJ/$$mol, $$\Delta H_f^\circ(C_6H$$_{12}$$O_6(s)) = -1273.3 kJ/$$mol, calculate $$\Delta H^\circ$$ for the fermentation of glucose: $$C_6H_{12}O_6$(s) \rightarrow 2 C_2H_5OH(l) + 2 CO_2$(g).$$

Accepted Answer

$$\Delta H^\circ = -69.2\ \mathrm{kJ}$$

Question 15

Which of the following is a correct application of Hess's Law?

Accepted Answer

The enthalpy change for a reaction is independent of the pathway and can be calculated by summing the enthalpy changes of individual steps.

Question 16

Which of the following is NOT a unit of energy?

Accepted Answer

Mole (mol)

Question 17

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

Accepted Answer

The reaction is exothermic and $$\Delta H \u003c 0.$$

Question 18

Which of the following best describes the difference between heat and temperature?

Accepted Answer

Heat is the transfer of thermal energy, while temperature is a measure of the average kinetic energy of particles.

Thermochemistry and Energy in Chemical Reactions (CHY 102)

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