Use the value of enthalpy you determined for CaCl2 to calculate what quantity of salt will be needed to make a chemical hot pack.

The Fundamentals of Calorimetry

Student Name

Date

Purpose

Procedure

Experimental Data

Table 1

Time (min)	Trial 1 Temp. °C	Trial 2 Temp. °C
1
2
3
4
5
6
7
8
9
10

Insert graph of the data from Data Table 1, plotting temperature vs. time, and use the Y intercept to find the temperature at time 0 when the two volumes of water are mixed.

Table 2

	Trial 1 (include units)	Trial 2 (include units)	Calculations (for Trial 1)
Initial temperature of cold water
Initial temperature of warm water
Temperature at time 0 from graph, T0
Heat lost by hot water
Heat gained by cold water
Heat gained by calorimeter
Temperature change of calorimeter
Heat capacity of calorimeter
Average Heat capacity of calorimeter

Table  3

Report data with correct units.  Show calculations below the table

	5g CaCl2	10g CaCl2	15g CaCl2	5g NH4Cl	10g NH4Cl	15g NH4Cl
Mass of water
Mass of salt
Moles of salt
Initial Temperature
Final Temperature
Change in Temperature
Heat released/absorbed by water
Heat released/absorbed by the calorimeter
Enthalpy of solution
Molar Enthalpy of solution
Average molar enthalpy of solution

Show calculations for first column:

Moles of salt

Heat released/absorbed by the solution

Heat released/absorbed by the calorimeter

Enthalpy of solution (J)

Enthalpy of solution (kJ)

Molar Enthalpy of solution

Average molar enthalpy of solution

Insert graphs of ΔT vs. grams of salt for NH4Cl

Lab Questions

What sort of relationship exists between the temperature change and the mass of the salt dissolved? Explain your answer.

The actual molar enthalpy of solution for calcium chloride is -81.3 kJ/mol, whereas the molar enthalpy of solution of ammonium chloride is 14.8 kJ/mol. Calculate the percent error of your results. Show the calculations.

Use the value of enthalpy you determined for CaCl2 to calculate what quantity of salt will be needed to make a chemical hot pack. Assume using 100 g (100 mL) of water and changing the temperature from 25 °C to 60 °C. Show all calculations.

Use the graph you drew for NH4Cl to determine the amount of salt needed to make a chemical cold pack. Assume using 100 g (100 mL) of water. The temperature should go down to 3.0 °C from a room temperature of 25 °C. Show all calculations.

Suggest practical ways in which the calorimeter or lab protocol could be improved to decrease percent errors.