Question 1

Which of the following statements correctly describes an exothermic reaction?

Accepted Answer

The system releases heat to the surroundings, and $$q is $$negative.

Question 2

A chemical system releases 200 kJ of heat and does 35 kJ of work on its surroundings. What are the signs of $$q$$ and $$w$$ for the system?

Accepted Answer

$$q is $$negative, $$w is $$positive

Question 3

Which equation correctly represents the change in enthalpy ($$\Delta H) $$for a chemical reaction?

Accepted Answer

$$\Delta H = H_{products} - H_{reactants}$$

Question 4

If work is done ONTO the system and heat LEAVES the system, what are the signs of $$w$$ and $$q$$?

Accepted Answer

$$w is $$positive, $$q is $$negative

Question 5

Which of the following best describes heat capacity?

Accepted Answer

The amount of energy required to raise the temperature of a given amount of substance by 1 degree Celsius.

Question 6

Water has a higher specific heat than iron. What does this mean in practical terms?

Accepted Answer

It takes more energy to raise the temperature of water than iron.

Question 7

Which of the following is true about the standard enthalpy of formation for $$O_2(g$$)$$?

Accepted Answer

It is zero because $$O_2(g$$)$$ is in its elemental form.

Question 8

Which formula is used to calculate the heat absorbed or released in a calorimetry experiment at constant pressure?

Accepted Answer

$$q = mC\Delta T$$

Question 9

If 4.50 grams of methane ($$CH_4) $$are combusted and the enthalpy of combustion is $$-890 kJ/$$mol, how much heat is released?

Accepted Answer

$$-250 kJ$$

Question 10

Which statement about Hess's Law is correct?

Accepted Answer

The enthalpy change of a reaction is independent of the pathway and depends only on the initial and final states.

Question 11

Which of the following is the correct reaction for the standard enthalpy of formation of sodium carbonate ($$Na_2CO_3$$)?

Accepted Answer

$$2Na(s) + C(graphite) + 1.5O_2(g) \rightarrow Na_2CO_3(s)$$

Question 12

Which of the following is NOT a correct statement about bond enthalpy?

Accepted Answer

Bond enthalpy is the energy released when a bond is formed.

Question 13

Using bond energies, calculate the enthalpy change ($$\Delta H) $$for the reaction: $$2H_2 + O_2$ \rightarrow 2H_2O. $$Given: $$D(H-H) = 436 kJ/$$mol, $$D(O=O) = 498 kJ/$$mol, $$D(O-H) = 463 kJ/$$mol.

Accepted Answer

$$-485 kJ$$

Question 14

Which of the following is true about measuring enthalpy change in a bomb calorimeter?

Accepted Answer

You are measuring internal energy change, not enthalpy change.

Question 15

Which of the following is the correct expression for the enthalpy change of a reaction using bond energies?

Accepted Answer

$$\Delta H = \sum D_{bonds\,broken} - \sum D_{bonds\,formed}$$

Question 16

A solution increases in temperature from 21.0°C to 27.5°C. If the mass of the solution is 100 g and its specific heat is $$4.18 	ext{ J/g} \cdot 	ext{K}$$, how much heat was absorbed?

Accepted Answer

$$2,730 J$$

Question 17

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

Accepted Answer

Enthalpy

Question 18

Which of the following reactions is endothermic?

Accepted Answer

A reaction where $$\Delta H \u003e 0$$

Question 19

Which of the following is the correct definition of the standard enthalpy of formation?

Accepted Answer

The enthalpy change when 1 mole of a compound is formed from its elements in their standard states.

Enthalpy, Calorimetry, and Bond Enthalpies: Study Notes for General Chemistry

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