AP Chem Unit 6.4: Heat Capacity and Calorimetry

A 1.0 g sample of a cashew was burned in a calorimeter containing 1000. g of water, and the temperature of the water changed from 20.0°C to 25.0°C. In another experiment, a 3.0 g sample of a marshmallow was burned in a calorimeter containing 2000. g of water, and the temperature of the water changed from 25.0°C to 30.0°C. Based on the data, which of the following can be concluded about the energy content for 1.0 g of each of the two substances? (The specific heat of water is 4.2 J/(g⋅°C).)

The combustion of 1.0 g of cashew releases more energy than the combustion of 1.0 g of marshmallow.

The heating curve for a sample of pure ethanol is provided above. The temperature was recorded as a 50.0 g sample of solid ethanol was heated at a constant rate. Which of the following explains why the slope of segment T is greater than the slope of segment R?

The specific heat capacity of the gaseous ethanol is less than the specific heat capacity of liquid ethanol.

AgNO3(aq) + NaC1(aq)→ AgC1(s) + NaNO3(aq) In an experiment a student mixes a 50.0 mL sample of 0.100 M AgNO3(aq) with a 50.0 mL sample of 0.100 M NaCl(aq) at 20.0°C in a coffee-cup calorimeter. Which of the following is the enthalpy change of the precipitation reaction represented above if the final temperature of the mixture is 21.0°C? (Assume that the total mass of the mixture is 100. g and that the specific heat capacity of the mixture is 4.2 J/(g °C).)

−84 kJ/molrxn

For an experiment, 50.0g of H2O was added to a coffee-cup calorimeter, as shown in the diagram above. The initial temperature of the H2O was 22.0°C, and it absorbed 300.J of heat from an object that was carefully placed inside the calorimeter. Assuming no heat is transferred to the surroundings, which of the following was the approximate temperature of the H2O after thermal equilibrium was reached? Assume that the specific heat capacity of H2O is 4.2J/(g⋅K).

23.4°C

A student mixes 50mL of 1.0MHCl and 50mL of 1.0MNaOH in a coffee-cup calorimeter and observes the change in temperature until the mixture reaches thermal equilibrium. The initial and final temperatures (°C) of the mixture are shown in the diagram above of the laboratory setup. Based on the results, what is the change in temperature reported with the correct number of significant figures?

5.5°C

A hot iron ball is dropped into a 200. g sample of water initially at 50°C. If 8.4 kJ of heat is transferred from the ball to the water, what is the final temperature of the water? (The specific heat of water is 4.2 J/(g·°C).)

60°C