31. Which statement is true for an exothermic process?

• A) The surroundings absorb heat
• B) The system absorbs heat
• C) The surroundings release heat
• D) Heat is absorbed and released equally
• Answer: A

32. In a calorimeter, the heat of reaction is measured by:

• A) The change in mass
• B) The change in temperature
• C) The change in volume
• D) The change in pressure
• Answer: B

33. Which of the following reactions is exothermic?

• A) Melting of ice
• B) Evaporation of water
• C) Combustion of ethanol
• D) Dissociation of NaCl
• Answer: C

34. The heat of vaporization refers to:

• A) The heat absorbed when a liquid changes to gas
• B) The heat released during combustion
• C) The heat required for a reaction to start
• D) The heat change during freezing
• Answer: A

35. The heat of reaction at constant pressure is known as:

• A) Work done
• B) Enthalpy change
• C) Entropy change
• D) Free energy change
• Answer: B

36. Which of the following methods can determine the heat of reaction?

• A) Hess’s Law
• B) Calorimetry
• C) Thermogravimetry
• D) All of the above
• Answer: D

37. An endothermic reaction occurs when:

• A) The products have less energy than the reactants
• B) The products have more energy than the reactants
• C) The temperature of the surroundings increases
• D) Energy is released to the surroundings
• Answer: B

38. The standard enthalpy change of a reaction is measured under which conditions?

• A) 1 atm pressure and 25°C
• B) 1 atm pressure and 100°C
• C) 0°C and 1 atm pressure
• D) 100°C and 1 atm pressure
• Answer: A

39. The heat change in a reaction is called:

• A) Free energy change
• B) Entropy change
• C) Enthalpy change
• D) Work done
• Answer: C

40. Which of the following best describes a calorimeter?

• A) An instrument that measures heat change
• B) An instrument that measures volume change
• C) An instrument that measures pressure change
• D) An instrument that measures mass change
• Answer: A