Q: A student mixes 50 mL of 0.100 M AgNO$$_3$$ and 50 mL of 0.100 M HCl in a constant pressure calorimeter. The temperature rises from 22.30 $$^\circC to 23.11$$ $$^\circC. If $$the calorimeter constant is 335 J/$$^\circC$$, what is the total heat absorbed by the solution?

$$335 \times (23.11 - 22.30) = 270.85 J$$

Q: Which equation correctly represents the relationship between heat ($$q$$), mass ($$m$$), specific heat ($$c$$), and temperature change ($$\Delta T$$)?

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

Question 1

Which of the following best describes the enthalpy change ($$\Delta H) $$for an exothermic reaction?

Accepted Answer

$$\Delta H is $$negative and heat is released from the system.

Question 2

A constant pressure calorimeter is used to measure the enthalpy change of a reaction. Which of the following is TRUE about the measurement?

Accepted Answer

It directly measures the enthalpy change ($$\Delta H) of $$the reaction.

Question 3

Given the reaction: $$2H_2(g) + 2Cl_2(g) \rightarrow 4HCl(g)$$, $$\Delta H^\circ = -92.3 kJ. $$What is the $$\Delta H^\circ if $$the equation is reversed?

Accepted Answer

$$\Delta H^\circ = +92.3 kJ$$

Question 4

Which statement about the standard enthalpy of formation ($$\Delta H_f^\circ) is $$correct?

Accepted Answer

It is zero for any element in its most stable (standard) state.

Question 5

If the enthalpy change for a reaction is $$\Delta H$$, what happens to $$\Delta H if $$the reaction is multiplied by a factor of $$n$$?

Accepted Answer

$$\Delta H is $$multiplied by $$n.$$

Question 6

Which of the following is an example of an endothermic reaction?

Accepted Answer

$$Fe_{(s)} + 415.5 kJ$$ $$\rightarrow Fe_{(g)}$$

Question 7

A student mixes 50 mL of 0.100 M AgNO$$_3$$ and 50 mL of 0.100 M HCl in a constant pressure calorimeter. The temperature rises from 22.30 $$^\circC to 23.11$$ $$^\circC. If $$the calorimeter constant is 335 J/$$^\circC$$, what is the total heat absorbed by the solution?

Accepted Answer

$$335 	imes (23.11 - 22.30) = 270.85 J$$

Question 8

Which of the following statements about enthalpy is INCORRECT?

Accepted Answer

The enthalpy change for a reaction is always positive.

Question 9

Which equation correctly represents the relationship between heat ($$q$$), mass ($$m$$), specific heat ($$c$$), and temperature change ($$\Delta T$$)?

Accepted Answer

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

Question 10

Which of the following best describes the heat of vaporization?

Accepted Answer

The heat required to convert one mole of a compound from liquid to gas.

Question 11

Which of the following is TRUE about thermochemical equations?

Accepted Answer

They show both mass and energy changes in a reaction.

Question 12

For the reaction $$C_{(s)} + O_{2(g)} \rightarrow CO_{2(g)} + 394 kJ$$, what does the $$+394 kJ $$indicate?

Accepted Answer

The reaction is exothermic and releases 394 kJ.

Question 13

Which of the following would NOT affect the enthalpy change ($$\Delta H) of a $$reaction?

Accepted Answer

Changing the temperature at which the reaction occurs.

Question 14

If the enthalpy change for a reaction is $$-150 kJ$$, what is the enthalpy change for the reverse reaction?

Accepted Answer

$$+150 kJ$$

Question 15

Which of the following is a property of enthalpy?

Accepted Answer

It is an extensive property.

Question 16

A reaction has $$\Delta H = +200 kJ. $$Which statement is correct?

Accepted Answer

The reaction is endothermic and absorbs heat.

Question 17

Which device is best suited for measuring the enthalpy change of a reaction at constant pressure?

Accepted Answer

Constant pressure calorimeter

Question 18

Which of the following statements about the enthalpy of formation is FALSE?

Accepted Answer

It is always negative for all compounds.

Question 19

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

Accepted Answer

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

Thermodynamics and Thermochemistry: Heat, Enthalpy, and Calorimetry

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