Question 1

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

Accepted Answer

Energy can be transformed between different types, but the total energy is conserved.

Question 2

A chemical reaction in a beaker causes the beaker to feel cold to the touch. Which of the following statements is true about this reaction?

Accepted Answer

The reaction is endothermic and $$ \Delta H \u003e 0 .$$

Question 3

Which of the following is the correct formula for calculating the kinetic energy of a moving object?

Accepted Answer

$$ KE = \frac{1}{2} m v^2$ $$

Question 4

During a constant pressure calorimetry experiment, 100 g of water absorbs 836 J of heat, causing its temperature to rise by 2°C. What is the specific heat capacity of water based on this data?

Accepted Answer

$$ 4.18 \ \mathrm{J} \ g$$^{-1}$$ \ K$$^{-1}$$ $$

Question 5

Which of the following statements about enthalpy ($$ H ) is $$correct?

Accepted Answer

Enthalpy is the internal energy of a system at constant pressure.

Question 6

A reaction has $$ \Delta H = -150 \ \mathrm{kJ} . $$Which of the following is true?

Accepted Answer

The reaction is exothermic and releases heat to the surroundings.

Question 7

Which of the following best describes the system and surroundings in a chemical reaction performed in a beaker on a laboratory bench?

Accepted Answer

The system is the chemical reaction; the surroundings are everything else, including the beaker and bench.

Question 8

Which of the following equations correctly represents the relationship between internal energy, heat, and work?

Accepted Answer

$$ \Delta E = q + w $$

Question 9

A bomb calorimeter is used to measure the energy released by the combustion of a fuel. Which of the following is true about this process?

Accepted Answer

The reaction occurs at constant volume and measures $$ \Delta E .$$

Question 10

Which of the following is the correct expression for the enthalpy change of a reaction using standard enthalpies of formation?

Accepted Answer

$$ \Delta H_{\mathrm{rxn}}^\circ = \sum n \Delta H_f^\circ (\mathrm{products}) - \sum m \Delta H_f^\circ (\mathrm{reactants}) $$

Question 11

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

Accepted Answer

The $$ \Delta H_f^\circ  of an $$element in its standard state is defined as zero.

Question 12

A student dissolves ammonium nitrate in water and observes that the temperature of the solution decreases. Which of the following best explains this observation?

Accepted Answer

The dissolution is endothermic; heat is absorbed from the surroundings.

Question 13

Which of the following best describes the sign conventions for $$ q $$ and $$ w $$ for the system?

Accepted Answer

$$ q \u003e 0 $$ means the system gains heat; $$ w \u003e 0 $$ means work is done on the system.

Question 14

Which of the following is an example of potential energy?

Accepted Answer

A stretched rubber band.

Question 15

If the enthalpy change for the vaporization of water is $$ 44.0 \ \mathrm{kJ/mol} $$, what is the enthalpy change for the condensation of water vapor?

Accepted Answer

$$ -44.0 \ \mathrm{kJ/mol} $$

Question 16

A reaction is carried out in two steps. The enthalpy change for step 1 is $$ +50 \ \mathrm{kJ} $$ and for step 2 is $$ -30 \ \mathrm{kJ} . $$What is the overall enthalpy change for the reaction?

Accepted Answer

$$ +20 \ \mathrm{kJ} $$

Question 17

Which of the following best explains why the enthalpy change for a reaction depends on the physical state of the reactants and products?

Accepted Answer

Because different states have different amounts of stored energy.

Question 18

Which of the following is the correct formula for calculating the specific heat of a substance?

Accepted Answer

$$ 	ext{Specific Heat} = \frac{	ext{quantity of heat transferred (J)}}{	ext{grams of substance (g)} 	imes 	ext{temperature change (K)}} $$

Chapter 7: Thermochemistry – Energy Changes in Chemical Reactions

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