Exp. 10 Calorimetry: Determination of Specific Heat POSTLAB QUESTIONS 1· The bac

Question

Exp. 10 Calorimetry: Determination of Specific Heat POSTLAB QUESTIONS 1· The background section says that while heat is flowing from the test substance to the water and calorimeter, heat is also flowing out of the calorimeter to the surroundings. What experimental evidence do you have from the experiment that heat is flowing out of the calorimeter? 2. A student ran the experiment described above on both lead and magnesium. He found that the incre magn Explain your answer. ase in the water temperature in the calorimeter was much greater for than it was for lead. Which has the greater specific heat, magnesium or lead? esium 3. A student ran the experiment twice, using the same amount of copper both times. The he used water in the calorimeter. The second time he used automobile antifreeze, which has a specific heat of 2.41 J/g C. In which experiment did he obtain the higher final temperature in the calorimeter, with water or antifreeze? Explain your answer.

Explanation / Answer

Calorimeter experiment

1. When heat is flowing out of calorimeter to the surrounding, the final temperature observed would be lower than the actual temperature expected from the reaction. The dT would be lower, that is the enthalpy change for the reaction as calculated would also have lower value than the actual value.

2. The metal which has higher specific heat would show higher final temperature than the metal having lower specific heat. Therefore, magnesium in this case has a higher specific heat as compared to lead. The capacity to hold heat is greater for magnesium in this case and thus it needs lower het to raise its temperature, so when same amount of heat is supplied, magnesium takes up all the heat and raises the temperature more than lead.

3. When the student used automobile anti-freeze liquid instead of water, we would observe lower final temperature as compared to when water was used in the calorimeter. Anti-freeze liquid lowers the temperature and now more heat is needed to raise the temperature of the calorimeter content. The anti-freeze liquid takes up more heat to reach the same temperature as with less heat to water. This is apparent from the lower specific heat value of anti-freeze liquid as compared to water.

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