Q: If the enthalpy of formation for $$CO_2(g$$)$$ is -393.5$$ \text{ kJ}$$ and for CO(g$$)$$ is -110.5$$ \text{ kJ}$$, what is the enthalpy change for the reaction CO(g$$) + \frac{1}{2} $$O_2(g$$) \rightarrow $$CO_2(g$$)$$?

$$\Delta H = -283.0 \text{ kJ}$$

Question 1

Which of the following best describes the study of thermochemistry?

Accepted Answer

The study of heat released or absorbed during chemical reactions.

Question 2

Which equation correctly represents the change in internal energy ($$\Delta E) of a $$system?

Accepted Answer

$$\Delta E = q + w$$

Question 3

A system absorbs 150 J of heat from the surroundings and does 40 J of work on the surroundings. What is the change in internal energy ($$\Delta E) of $$the system?

Accepted Answer

$$\Delta E = 110 	ext{ J}$$

Question 4

Which of the following is a state function?

Accepted Answer

Enthalpy ($$H)$$

Question 5

The enthalpy change of a reaction ($$\Delta H_{rxn}) is $$given by which equation?

Accepted Answer

$$\Delta H_{rxn} = H_{final} - H_{initial}$$

Question 6

Which statement is true about exothermic reactions?

Accepted Answer

They release heat to the surroundings.

Question 7

Calculate the heat ($$q) $$required to raise the temperature of 35.0 g of Al from 55.0°C to 75.0°C. The specific heat of Al is $$0.908 	ext{ J/g} \cdot 	ext{°C}.$$

Accepted Answer

$$q = 636 	ext{ J}$$

Question 8

Which of the following is NOT true about specific heat?

Accepted Answer

It is the same for all substances.

Question 9

According to the first law of thermodynamics, which of the following is always true?

Accepted Answer

$$\Delta E_{universe} = 0$$

Question 10

Which of the following reactions is exothermic?

Accepted Answer

A reaction where $$\Delta H is $$negative.

Question 11

If a chemical reaction has $$\Delta H = -393.5 	ext{ kJ}$$, what does this indicate?

Accepted Answer

The reaction is exothermic and releases 393.5 kJ of energy.

Question 12

Which equation is used to calculate the heat absorbed or released by a substance?

Accepted Answer

$$q = mC_s \Delta T$$

Question 13

Which of the following is an example of a state function?

Accepted Answer

Energy

Question 14

In a chemical reaction, which process is associated with absorbing energy?

Accepted Answer

Bond breaking

Question 15

Which law allows you to add the enthalpy changes of multiple reactions to find the overall enthalpy change?

Accepted Answer

Law of Hess

Question 16

If the enthalpy of formation for $$CO_2(g$$)$$ is -393.5$$ 	ext{ kJ}$$ and for CO(g$$)$$ is -110.5$$ 	ext{ kJ}$$, what is the enthalpy change for the reaction CO(g$$) + \frac{1}{2} $$O_2(g$$) ightarrow $$CO_2(g$$)$$?

Accepted Answer

$$\Delta H = -283.0 	ext{ kJ}$$

Question 17

Which of the following statements about calorimetry is correct?

Accepted Answer

It measures the amount of heat transferred during a chemical reaction.

Question 18

A reaction has $$\Delta H = +75 	ext{ kJ}. $$What does this mean?

Accepted Answer

The reaction is endothermic and absorbs 75 kJ of energy.

Question 19

Which of the following best explains why specific heat is unique to each substance?

Accepted Answer

Because each substance has a different molecular structure and bonding.

Thermochemistry and Enthalpy: Study Notes for General Chemistry

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