Using Hess's law to calculate enthalpy change

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Chemistry lab report (5)

Using Hess law to calculate enthalpy change

Aim: To calculate the enthalpy change for the reaction of:

(MgSO4(s) + 7H2O         MgSO4.7H2O(s) )

Hypothesis: The literature value according to research is -104 Kj/mol

Variables:

Dependant variable: The final temperature of the solution

Independent variable: ---------------------------------

Controlled variables: - Mass of water

                                   - Mass of magnesium sulphate anhydrous

                                   - Mass of MgSO4.7H20

Materials:

1) Safety spectacles

2) 2 filter papers

3) Spatula

4) Digital balance

5) 2 polystyrene cups

6) Thermometer

7) Magnesium sulphate anhydrous

8) Magnesium sulphate-7- water

9) Distilled water

10) Measuring cylinder

Procedure:

Part A

1) Weigh 3.01g of MgSO4 anhydrous to the nearest 0.01g on a filter paper, using the digital balance.

2) Weigh 45.00g of water to the nearest 0.01g into a polystyrene cup using the balance.

3) Measure the initial temperature of the measured amount of water using the thermometer and record this value.

4) Add the measured amount of MgSO4 anhydrous to the water and stir. Measure and record the maximum temperature obtained using the thermometer.

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Part B

1) Weigh 6.16g of MgSO4.7H20 to the nearest 0.01g on a filter paper, using the digital balance.

2) Weigh 41.85g of water to the nearest 0.01g into a polystyrene cup using the balance.

3) Measure the initial temperature of the measured amount of water using the thermometer and record this value.

4) Dissolve the MgSO4.7H20 in the water and record the temperature change associated with this process.

 

Results:

Discussion:

*First the enthalpy change of the reaction in part A is calculated:

(MgSO4(s)  + 100H2O(l)                      ...

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