Heat Transfer and Calorimetry

A 1.0mol sample of He(g) at 25°C is mixed with a 1.0mol sample of Xe(g) at 50°C. Which of the following correctly predicts the changes in average kinetic energy and the average speed of the Xe(g) atoms that will occur as the mixture approaches thermal equilibrium?

Average Kinetic Energy of XeAtomsAverage Speed of Xe Atoms Will decrease Will decrease

Which of the following is a list of the minimum amount of data needed for determining the molar enthalpy of solution of KCl(s) in pure H2O(l) ? (Assume that the KCl(aq) has the same specific heat capacity as pure water and that the initial temperatures of the KCl(s) and the water are the same.)

Mass of KCl(s), mass of H2O, initial temperature of the water, and final temperature of the solution

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.

A 50.0 g sample of Fe at 100°C is added to 500.0 mL of water at 35°C in a perfectly insulated container. Which of the following statements is true?

The heat energy lost by the Fe will be equal to the heat energy gained by the water.

A 100 g sample of a metal was heated to 100oC and then quickly transferred to an insulated container holding 100 g of water at 22oC. The temperature of the water rose to reach a final temperature of 35oC. Which of the following can be concluded?

The metal temperature changed more than the water temperature did, but the metal lost the same amount of thermal energy as the water gained.

A 10. g cube of copper at a temperature T1 is placed in an insulated cup containing 10. g of water at a temperature T2 . If T1 > T2, which of the following is true of the system when it has attained thermal equilibrium? (The specific heat of copper is 0.385 J/(g·°C) and the specific heat of water is 4.18 J/(g·°C).)

The temperature of the copper changed more than the temperature of the water.

NaOH(aq) + HCl(aq) → H2O(l) + NaCl(aq) A student is trying to determine the heat of reaction for the acid-base neutralization reaction represented above. The student uses 0.50 M NaOH and 0.50 M HCl solutions. Which of the following situations, by itself, would most likely result in the LEAST error in the calculated value of the heat of reaction?

The thermometer was incorrectly calibrated and read 0.5 Celsius degree too high during the procedure.

A student conducted an experiment to determine for the reaction between HCl(aq) and NaOH(aq). The student ran two trials using the volumes of HCl(aq) and NaOH(aq) indicated in the table above, and determined the amount of heat released. Which of the following best explains the relationship between X and Y?

Y = X, because the number of moles of acid and base reacting with each other is the same in both trials.

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 MNaCl(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

When 5.0 g of NH4ClO4(s) is added to 100. mL of water in a calorimeter, the temperature of the solution formed decreases by 3.0°C. If 5.0 g of NH4ClO4(s) is added to 1000. mL of water in a calorimeter initially at 25.0°C, the final temperature of the solution will be approximately

24.7°C

In an insulated cup of negligible heat capacity, 50. g of water at 40.°C is mixed with 30. g of water at 20.°C. The final temperature of the mixture is closest to

33°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