Holt Ch 16

Open Ended

What is one concept from thermochemistry that you found most interesting or would like to learn more about?

Multiple Choice

Which of the following is NOT an objective of studying thermochemistry as listed in the slide?

• Define temperature and state the units in which it is measured.

• Explain enthalpy change, enthalpy of reaction, enthalpy of formation, and enthalpy of combustion.

• Perform specific-heat calculations.

• Describe the structure of an atom.

Open Ended

Why is understanding thermochemistry important in everyday life?

Multiple Choice

What does thermochemistry study?

• The transfer of energy as heat during chemical and physical changes

• The structure of atoms

• The rate of chemical reactions

• The classification of elements

Multiple Select

Which of the following statements about calorimeters and heat measurement are correct?

• A calorimeter measures the energy absorbed or released as heat in a chemical or physical change.

• Reactants in a calorimeter are sealed in a reaction chamber immersed in water.

• The temperature change of water in a calorimeter is used to calculate the energy as heat given off by a reaction.

• A calorimeter measures the mass of reactants.

Multiple Choice

Which of the following is the correct unit for specific heat?

• J/(g·°C)

• J/(mol·K)

• W/(m·K)

• kg/(m·s²)

Open Ended

Explain how the specific heat of a substance affects the amount of energy transferred as heat during a temperature change.

Multiple Choice

Which compound listed in the table has the highest molar heat capacity?

• Octane, C8H18(l)

• Aluminum chloride, AlCl3(s)

• Water, H2O(l)

• Barium chloride, BaCl2(s)

Multiple Choice

Which of the following best describes an exothermic reaction?

• A reaction that releases energy and has products with less energy than the reactants.

• A reaction that absorbs energy and has products with more energy than the reactants.

• A reaction in which the enthalpy change is positive.

• A reaction that does not involve any energy change.

Open Ended

Explain how you would determine the specific heat of an unknown substance using experimental data.

Multiple Select

Which of the following statements about specific heat are correct based on the equation cp = q / (m × ΔT)?

• Specific heat depends on the mass of the sample.

• Specific heat is the amount of energy required to raise the temperature of 1 gram of a substance by 1 K.

• The equation can be rearranged to solve for energy gained or lost.

• q represents the energy lost or gained.

Multiple Select

Which statements about thermochemical equations are correct?

• They include the quantity of energy released or absorbed as heat.

• Chemical coefficients represent numbers of moles.

• They always show the energy as a reactant.

• They describe the physical states of reactants and products.

Multiple Choice

How much energy will the 4.0 g glass sample gain when heated from 314 K to 344 K?

• 24 J

• 32 J

• 20 J

• 40 J

Open Ended

Describe the difference between enthalpy and enthalpy change, and explain why only changes in enthalpy can be measured.

Multiple Choice

For an exothermic reaction, what is the sign of ΔH and why?

• Negative, because the system loses energy.

• Positive, because the system gains energy.

• Zero, because there is no energy change.

• It can be either positive or negative.

Open Ended

Describe what the energy diagram of an exothermic reaction shows about the energy changes during the reaction.

Multiple Choice

Which of the following statements best describes an endothermic reaction as shown in the diagram?

• Energy is released and ΔH is negative.

• Energy is absorbed and ΔH is positive.

• Energy is released and ΔH is positive.

• Energy is absorbed and ΔH is negative.

Open Ended

Describe how the enthalpy of formation is used to write a thermochemical equation for the formation of a compound from its elements in their standard states.

Multiple Choice

Which of the following compounds is likely to be more stable based on its enthalpy of formation?

• A compound with a large positive enthalpy of formation

• A compound with a large negative enthalpy of formation

• A compound with zero enthalpy of formation

• A compound with a small positive enthalpy of formation

Multiple Select

Select all statements that are true about compounds with positive values of enthalpy of formation.

• They are typically unstable.

• They decompose easily at room temperature.

• They are more stable than their elements.

• Their ΔHf° values are negative.

Open Ended

Explain the difference between the enthalpy of formation and the enthalpy of combustion, including how each is defined in terms of reactants and products.