Postlab 8
1. Use data from the 4 calibration trials to calculate the average heat capacity, Ccal, of your
calorimeter. Use a Grubbs test to identify outliers. Calculate the standard deviation and 95%
confidence interval using the remaining data points.
- Ccal (kJ/Celsius)
Trial 1- 372.18
Trial 2- 305.78
Trial 3- 328.76
Trial 4- 314.98
Sample Calculation-
2. Use data from the ammonium nitrate dissolution experiment to calculate the heat of solution in
kJ/mol. Use a Grubbs test to identify outliers. Calculate the standard deviation and 95% confidence
interval using the remaining data points.
-Ccal (kJ/Celsius)
Trial 1- 0.31
Trial 2- 0.67
Trial 3- 0.073
Trial 4- 0.32
3. Look up the literature value for the heat of solution of ammonium nitrate and compare this with
your measured value. What was your % error? What are likely causes for this deviation in your
result?
The literature value of ammonium nitrate is 25.7 kJ/mol was much higher than the calculated value.
The % error is above 100 which shows that there is a huge error in the data set. It could have been
better to record the minimum temperature right away rather than waiting for a long period of time.
4. Calculate the average efficiency of your calorimeter (% of heat absorbed by the water in the
calorimeter relative to the amount of heat produced by dissolving the ammonium nitrate) including
95% confidence limits. Use the literature value for the heat of solution. For the purpose of this
calculation, neglect the heat absorbed by the Thermos®.
Efficacy= 1.45%
Mean= 1.267
Standard deviation = 0.127
95% CI = 1.267±0.0876 (±7.12%)
5. Write an abstract for this experiment. An abstract is a brief (one paragraph or less) description of
the goal and results of the experiment.
Using a calorimeter and certain known values, such as the specific heat of water, the experimenters
attempted to determine the heat of reaction of ammonium nitrate dissolution in water. In order to
determine how much heat a Thermos® calorimeter absorbed during a heat transfer, hot water and
cold water were used in a calibration process. Following the determination of the Thermos®
calorimeter's heat capacity, fresh water and ammonium nitrate were poured into the device, with
the pre- and post-reaction temperatures recorded. Since ammonium nitrate absorbs heat from the
surrounding water, a positive heat of reaction is to be predicted from its usage in cold packs. The
heat of reaction was calculated using the temperature measurements and the Thermos®
calorimeter's heat capacity; the result was 0.34 ± 0.2129 kJ/mol, which is not close to the literature
value of 25.7 kJ/mol and suggests that the process was highly inaccurate and could be improved in
several ways.