1. What does thermochemistry study?
a) The rates of chemical reactions
b) The energy changes associated with chemical reactions
c) The equilibrium positions of reactions
d) The types of chemical bonds
Answer: b) The energy changes associated with chemical reactions
2. What is the primary unit of energy used in thermochemistry?
a) Watt
b) Joule
c) Celsius
d) Mole
Answer: b) Joule
3. What is enthalpy?
a) The measure of heat flow at constant pressure
b) The measure of temperature change
c) The amount of work done by the system
d) The amount of energy required to ionize an atom
Answer: a) The measure of heat flow at constant pressure
4. What is the term for the heat absorbed or released during a chemical reaction?
a) Enthalpy change
b) Activation energy
c) Free energy
d) Bond dissociation energy
Answer: a) Enthalpy change
5. What is the standard enthalpy of formation?
a) The enthalpy change when one mole of a compound is formed from its elements in their standard states
b) The enthalpy change when a substance is dissolved in water
c) The enthalpy change when a substance is burned in oxygen
d) The enthalpy change when a reaction reaches equilibrium
Answer: a) The enthalpy change when one mole of a compound is formed from its elements in their standard states
6. What is the heat of combustion?
a) The heat released when one mole of a substance reacts with oxygen
b) The heat absorbed when one mole of a substance is formed
c) The heat required to vaporize one mole of a substance
d) The heat released when one mole of a substance dissolves in water
Answer: a) The heat released when one mole of a substance reacts with oxygen
7. What does Hess’s Law state?
a) The total enthalpy change for a reaction is the sum of the enthalpy changes for each step of the reaction
b) The enthalpy change of a reaction is independent of the temperature
c) The enthalpy change of a reaction is equal to the activation energy
d) The enthalpy change of a reaction depends on the pressure
Answer: a) The total enthalpy change for a reaction is the sum of the enthalpy changes for each step of the reaction
8. What is the term for the energy required to break one mole of bonds in gaseous molecules?
a) Bond dissociation energy
b) Heat of formation
c) Enthalpy change
d) Activation energy
Answer: a) Bond dissociation energy
9. What is an exothermic reaction?
a) A reaction that absorbs heat from the surroundings
b) A reaction that releases heat to the surroundings
c) A reaction that does not involve any heat change
d) A reaction that occurs only at high temperatures
Answer: b) A reaction that releases heat to the surroundings
10. What is an endothermic reaction?
a) A reaction that releases heat to the surroundings
b) A reaction that absorbs heat from the surroundings
c) A reaction that produces light
d) A reaction that occurs only in the dark
Answer: b) A reaction that absorbs heat from the surroundings
11. What is the term for the heat required to raise the temperature of one mole of a substance by one degree Celsius?
a) Specific heat capacity
b) Molar heat capacity
c) Heat of vaporization
d) Heat of fusion
Answer: b) Molar heat capacity
12. What does the term “entropy” refer to in thermochemistry?
a) The measure of the randomness or disorder of a system
b) The measure of energy required to initiate a reaction
c) The measure of heat absorbed or released
d) The measure of the rate of a reaction
Answer: a) The measure of the randomness or disorder of a system
13. What is the relationship between enthalpy and entropy in determining the spontaneity of a reaction?
a) A reaction is spontaneous if enthalpy is positive and entropy is negative
b) A reaction is spontaneous if enthalpy is negative and entropy is positive
c) A reaction is spontaneous if both enthalpy and entropy are negative
d) A reaction is spontaneous if both enthalpy and entropy are positive
Answer: b) A reaction is spontaneous if enthalpy is negative and entropy is positive
14. What does the term “free energy” refer to in thermochemistry?
a) The energy available to do work in a system at constant temperature and pressure
b) The energy required to break chemical bonds
c) The energy stored in chemical bonds
d) The energy released during a phase change
Answer: a) The energy available to do work in a system at constant temperature and pressure
15. What is the heat of vaporization?
a) The heat required to convert a liquid into a gas at its boiling point
b) The heat released when a gas condenses into a liquid
c) The heat absorbed during the melting of a solid
d) The heat released during the freezing of a liquid
Answer: a) The heat required to convert a liquid into a gas at its boiling point
16. What is the heat of fusion?
a) The heat absorbed during the melting of a solid
b) The heat required to convert a liquid into a gas
c) The heat released when a gas condenses into a liquid
d) The heat released during the freezing of a liquid
Answer: a) The heat absorbed during the melting of a solid
17. What is a calorimeter used for?
a) To measure the rate of a reaction
b) To measure the concentration of reactants
c) To measure the heat absorbed or released during a reaction
d) To measure the volume of gases
Answer: c) To measure the heat absorbed or released during a reaction
18. What is the principle of a bomb calorimeter?
a) It measures the heat released during a combustion reaction
b) It measures the heat absorbed during a phase change
c) It measures the temperature change of a liquid
d) It measures the pressure of a gas
Answer: a) It measures the heat released during a combustion reaction
19. What does the term “heat capacity” refer to?
a) The amount of heat required to raise the temperature of a substance by one degree Celsius
b) The amount of heat absorbed during a chemical reaction
c) The amount of heat released during a phase change
d) The energy required to break chemical bonds
Answer: a) The amount of heat required to raise the temperature of a substance by one degree Celsius
20. What does the second law of thermodynamics state?
a) Energy cannot be created or destroyed
b) The entropy of the universe always increases for a spontaneous process
c) The enthalpy change is always zero for a spontaneous process
d) The free energy of a system is always constant
Answer: b) The entropy of the universe always increases for a spontaneous process
21. What does a negative enthalpy change indicate about a reaction?
a) The reaction is endothermic
b) The reaction is exothermic
c) The reaction is at equilibrium
d) The reaction has a high activation energy
Answer: b) The reaction is exothermic
22. What does a positive entropy change indicate about a reaction?
a) The reaction leads to a decrease in disorder
b) The reaction leads to an increase in disorder
c) The reaction is endothermic
d) The reaction has a high activation energy
Answer: b) The reaction leads to an increase in disorder
23. What does the term “enthalpy of solution” refer to?
a) The heat absorbed or released when a substance dissolves in a solvent
b) The heat required to convert a liquid into a gas
c) The heat released during a combustion reaction
d) The heat absorbed during the melting of a solid
Answer: a) The heat absorbed or released when a substance dissolves in a solvent
24. What is the main factor that determines whether a reaction is spontaneous at constant temperature and pressure?
a) Enthalpy change
b) Entropy change
c) Activation energy
d) Heat capacity
Answer: b) Entropy change
25. What is the term for a process that absorbs heat from the surroundings and is characterized by a positive enthalpy change?
a) Endothermic process
b) Exothermic process
c) Isothermal process
d) Adiabatic process
Answer: a) Endothermic process
26. What does the term “thermochemical equation” refer to?
a) A chemical equation that includes the enthalpy change of the reaction
b) A chemical equation that shows the rate of reaction
c) A chemical equation that describes the equilibrium position
d) A chemical equation that measures the concentration of reactants
Answer: a) A chemical equation that includes the enthalpy change of the reaction
27. What is the primary purpose of using a standard state in thermochemistry?
a) To compare the enthalpy changes of different reactions under uniform conditions
b) To measure the concentration of solutions
c) To calculate the rate of reaction
d) To determine the volume of gases
Answer: a) To compare the enthalpy changes of different reactions under uniform conditions
28. What does the term “enthalpy of reaction” refer to?
a) The heat absorbed or released during a chemical reaction
b) The energy required to break chemical bonds
c) The heat required to raise the temperature of a substance
d) The energy needed to initiate a reaction
Answer: a) The heat absorbed or released during a chemical reaction
29. What is the term for a reaction that occurs without the need for an external energy source once initiated?
a) Spontaneous reaction
b) Non-spontaneous reaction
c) Endothermic reaction
d) Isothermal reaction
Answer: a) Spontaneous reaction
30. What is the impact of increasing temperature on an endothermic reaction?
a) It decreases the reaction rate
b) It increases the reaction rate
c) It has no effect on the reaction rate
d) It shifts the equilibrium position to favor reactants
Answer: b) It increases the reaction rate