Question 1

Which of the following best describes the process shown in the first image, where $$\Delta H = -1367\ \mathrm{kJ}$$ for the reaction $$\mathrm{C_2H_5OH}(\ell) + 3\mathrm{O_2$}(g) \rightarrow 2\mathrm{CO_2$}(g) + 3\mathrm{H_2O}(\ell)$$?

Accepted Answer

The reaction is exothermic because heat is released to the surroundings.

Question 2

A cyclist at the top of a hill (as shown in the second image) has high potential energy and zero kinetic energy. As the cyclist descends, what happens to the energies?

Accepted Answer

Potential energy decreases and kinetic energy increases.

Question 3

Given the equation for electrostatic potential energy $$E_{el} = \kappa \frac{Q_1$ Q_2$}{d}$$, which of the following statements is correct regarding the interaction between two like charges as their separation distance decreases?

Accepted Answer

The electrostatic potential energy increases, indicating stronger repulsion.

Question 4

In the piston system shown, which of the following best describes the type of system depicted?

Accepted Answer

Closed system: only energy can be exchanged with the surroundings.

Question 5

When boiling water on a stove (as shown in the image), what is the direction of heat flow?

Accepted Answer

Heat flows from the burner to the water.

Question 6

A thermos bottle is used to keep liquids hot or cold for extended periods. Which type of system does a thermos best approximate?

Accepted Answer

Isolated system

Question 7

According to the sign conventions for $$q$$, $$w$$, and $$\Delta E$$, which of the following scenarios results in a negative $$\Delta E$$ for a system?

Accepted Answer

The system releases heat and does work on the surroundings.

Question 8

Given the reaction $$\mathrm{C(graphite, s) + O_2$(g) \rightarrow CO_2$(g)}$$ with $$\Delta H_f^\circ (CO_2$) = -393.5\ \mathrm{kJ/mol}$$, what is the enthalpy change for the formation of one mole of $$CO_2(g$$)$$ from its elements in their standard states?

Accepted Answer

$$\Delta H = -393.5\ \mathrm{kJ}$$

Question 9

Which of the following is true about the enthalpy change ($$\Delta H) $$for a reaction and its reverse?

Accepted Answer

$$\Delta H$$ for the reverse reaction is equal in magnitude but opposite in sign to the forward reaction.

Question 10

A 60.0 g metal rod is heated to 100°C and placed in 40.0 g of water at 35.2°C. The final temperature is 52.1°C. If the specific heat of water is $$4.18\ \mathrm{J/g\cdot°C}$$, what is the specific heat ($$C_s) of $$the metal rod? (Assume no heat loss to surroundings.)

Accepted Answer

$$0.98\ \mathrm{J/g\cdot°C}$$

Question 11

Which of the following best describes the energy changes when a system absorbs heat from the surroundings and has work done on it by the surroundings?

Accepted Answer

$$q \u003e 0$$, $$w \u003e 0$$, $$\Delta E \u003e 0$$

Question 12

Which of the following is a state function?

Accepted Answer

The enthalpy change when a cube of sugar is oxidized to $$CO_2$$ and $$H_2O.$$

Question 13

A bomb calorimeter is used to measure the heat of combustion of a sample. If the heat capacity of the calorimeter is $$5.00\ \mathrm{kJ/°C}$$ and the temperature rises by $$2.00\ \mathrm{°C}$$, what is the heat released by the reaction?

Accepted Answer

$$-10.0\ \mathrm{kJ}$$

Question 14

Which of the following statements about specific heat capacity is correct?

Accepted Answer

Specific heat capacity is the amount of heat required to raise the temperature of 1 gram of a substance by 1°C.

Question 15

If $$50.0\ \mathrm{g} of $$water at $$25.0\ ^\circ\mathrm{C}$$ absorbs $$4180\ \mathrm{J} of $$heat, what is the final temperature of the water? (Specific heat of water is $$4.18\ \mathrm{J/g\cdot°C})$$

Accepted Answer

$$35.0\ ^\circ\mathrm{C}$$

Question 16

Which of the following best describes the relationship between $$\Delta H$$ and $$\Delta E$$ for a reaction involving gases?

Accepted Answer

$$\Delta H = \Delta E + (\Delta n)RT$$

Question 17

A reaction in a coffee-cup calorimeter causes the temperature of the solution to decrease. Which of the following is true?

Accepted Answer

The reaction is endothermic and $$q_{solution} is $$positive.

Question 18

Which of the following is the correct formula for calculating the amount of heat transferred to a substance?

Accepted Answer

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

Question 19

Which of the following best explains why water is used as a coolant in car engines?

Accepted Answer

Water has a high specific heat capacity, so it resists temperature changes.

Thermochemistry and Calorimetry: Study Notes for General Chemistry

Guida di studio - Domande di pratica

Study guide - Flashcard