Chemistry Internal Assessment Hesss Law

by lizzielunn817gmailcom (student)

International Baccalaureate Chemistry

Chemistry Internal Assessment

DCP and CE

“Hess’s Law”

2014

Raw data table:

Observations:

The solution with MgSO4 a white precipitate formed
In the experiment using MgSO4 the thermos got warm
The solution with MgSO4.7H2O turned a cloudy white
In the experiment using MgSO4.7H2O the thermos got cooler

Full Equations of Reactions

1) MgSO4(s) → Mg2+(aq) + SO42-(aq)

2) MgSO4.7H2O(s) → Mg2+(aq) + SO42-(aq) + 7H2O(l)

Literature Values

A Raw Data Table Showing the Relationship between Time Elapsed and the Temperature of the Reaction of Hydrous and Anhydrous Magnesium Sulphate using a logger pro temperature sensor.

Graphs from the experiment using MgSO4 showing temperature over time with a best fit line for the data points following the maximum temperature to allow us to calculate an extrapolated maximum temperature

Graphs from the experiment using MgSO4.7H2O showing temperature over time with a best fit line for the data points following the maximum temperature to allow us to calculate an extrapolated maximum temperature

Calculation of ΔH for MgSO4

Calculation of ΔH for MgSO4.7H2O

Hess’s Law

Conclusion

Hess’s Law is used to calculate the enthalpy change of a reaction that cannot be measured directly. Thus by calculating the enthalpy for two reactions I was able to calculate the enthalpy for a third. I then compared these values to their theoretical values. However the aim of this experiment was to calculate the enthalpy of the reaction between MgSO4 and water so my final answer is

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Our percentage error or ...