# Determinaing Enthalpy Change of Potassium

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Determinaing Enthalpy Change of Potassium
Determining the enthalpy change for the thermal decomposition of potassium hydrogen carbonate into potassium carbonate.
Controlled Variables: 1. Volume of HCl ± 0.5 cm3 (± 2%) 2. Concentration of HCl, 3. Same mass of K2CO3 and KHCO3 within specified ranges of 2.5 – 3.0g and 3.25 – 3.75g respectively 4. Same calorimeter used i.e. polystyrene cup is used in this experiment 5. Same thermometer will be used ± 0.10K 6. Same source of K2CO3, KHCO3 and HCl

Raw Data Results:
The raw data table shows, the temperatures at initial point, after and the change in temperature of the reaction between K2CO3(s) with HCl (aq)
The change in temperature is calculated as:
After temperature – initial temperature= change in temperature K2CO3 | The temperatures of each trial at ± 0.10K | Trials | Initial ± 0.5% | After ± 0.4% | Change ± 0.9% | 1 | 21.600 | 23.700 | -2.100 | 2 | 22.200 | 24.600 | -2.400 |

Therefore the Average can be calculated for the temperature:
The equation shows, Average = change in temperature of trials (1 + 2)/2
Therefore the Average = (-2.1 +( - 2.4))/2 = -2.250K ± 0.9%
The table below shows the raw data of the temperatures at their initial point, after and the change in temperature of the reaction between KHCO3 with HCl. KHCO3 | The temperatures of each trial at ± 0.10K | Trials | Initial ± 0.5% | After ± 0.7% | Change is ( + ) ± 1.2% | 1 | 21.700 | 14.300 | 7.4 | 2 | 22.000 | 14.200 | 7.8 |

The average can be calculated for the temperature by using the same equation as shown above. Therefore:
Average of the temperature change of KHCO3 = (7.4 + 7.8)/2 = 7.6 0K ± 1.2%
When using a thermometer that measures ± 0.1 K the uncertainty shown in the table of trial 1 for example, K2CO3 measures 21.7000K will equal to
(0.1/21.600) X 100 = ± 0.5% for trial 2:
(0.1/14.300) X 100 = ± 0.4 %
The overall uncertainty for K2CO3 for the temperature change is the summing up of all the uncertainties.
0.5 + 0.4 = ± 0.9% ( this

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