CH 11-4: Calorimetry and Molar Enthalpy

Use the following information about calorimetric data to answer the next question

1) maximum temperature change of water

2) mass of aluminum calorimeter

3) mass of aluminum calorimeter and water

4) initial temperature of aluminum calorimeter

5) maximum temperature change of ethanol

6) mass change of ethanol

The data above that you need to know to determine the molar heat of combustion for ethanol, listed in numerical order, are:

• 1356

• 1236

• 1345

• 1456

In an experiment, a student heated 500 g of water from 25.0 °C to 91.0 °C using 0.133 mol of ethanol. If it is assumed that all the heat energy was absorbed by the calorimeter water, the experimental molar enthalpy of combustion for ethanol was

+/- ___________ MJ/mol.

• 1.04

• 1.38

• 138

• 1.62

In a chemistry experiment, 12g of (NH₄)₂SO₄(s) was dissolved in 120mL of water in a simple calorimeter. A temperature change from 20.2°C to 17.8°C was observed. The experimental molar enthalpy of solution for ammonium sulfate was

• -13 kJ/mol

• -1.2 kJ/mol

• +1.2 kJ/mol

• +13 kJ/mol

Cold packs are used to treat sprains and bruises. A chemical commonly used in cold packs is ammonium nitrate, NH₄NO₃(s), which can produce a cooling effect. A student designed a calorimetery experiment to determine the energy change for the dissolving of ammonium nitrate and recorded the following results:

Heat capacity of calorimeter and water: 228 J/°C

Initial temperature of water: 21.6°C

Final temperature of water: 16.4°C

Mass of ammonium nitrate: 0.250 g

• 297 kJ

• 41.9 kJ

• 5.45 kJ

• 1.19 kJ

The calorimeter shown in the diagram to the left can be used to determine the specific heat capacity of copper. The calorimeter was at room temperature before the heated copper was added.

Two variables that could have been manipulated in this calorimetry experiment for additional trials are:

• I and II

• I and IV

• II and III

• II and IV