Hesss Law Lab, use Hesss law to find the enthalpy change of combustion of magnesium which is a highly exothermic reaction.

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Hess's Law Lab

Hess's Law

Hess's Law states that that the value of ?H for a reaction is the same whether it occurs directly or as a series of steps.

Purpose

To use the Hess's law to find the enthalpy change of combustion of magnesium which is a highly exothermic reaction.

Determining the enthalpy change for the reactions of Mg in HCl(aq) and MgO(s) HCl(aq) experimentally and alongside that use the enthalpy change for hydrogen gas (Table value) when it is combusted , to find the enthalpy change for the combustion of magnesium.

HYPOTHESIS

The heat of combustion for magnesium can be determined by determining the heat of reaction for the following reactions:

1) Mg(s) + 2HCl (aq) MgCl2(aq) + H2(g)

2) MgO(s) + 2HCl(aq) MgCl2(aq) + H2O(l)

3) H2(g) + 1/2 O2(g) H2O(l)

Once these values have been obtained, I can add or subtract these values in order to achieve the heat of combustion for magnesium.

Apparatus

Goggles

Lab apron

Electric balance

100 mL graduated cylinder

2 plastic foam cup