Enthalpy Change between Metal and Solution of Salt: An Experiment

685 Words Apr 9th, 2008 3 Pages
This experiment will test the suggestion that the enthalpy change between a metal and a solution of a salt is related to the relative position of the two metals in the reactivity. Presumably the further apart in the series the bigger the enthalpy change will be.

The experiment is as follows,

1) Zn(s) + CuSO4(aq) ZnSO4(aq) + Cu(s)
2) Zn(s) + Pb(NO3)2(aq) Zn(NO3)2 (aq) + Pb(s)

Both of the solutions will be in 1mol.dm-3

Apparatus:
Distilled Water
Polystyrene Cup
Polystyrene Lid for cup
Thermometer
1mol.dm-3 Copper Sulphate Solution
1mol.dm-3 Lead Nitrate Solution
Zinc
25cm3 Measuring Cylinder
Safety Goggles
Balance

Readings

For this experiment the readings that you will need to take are the
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The first thing to do is to calculate the change in temperature

Maximum temperature – initial temperature
30oC – 25oC = 5oC

Then we can go on to use the formula
ΔH = m x c x Δθ

ΔH = enthalpy change
M = mass (g)
C = specific heat capacity (J.deg-1.g-1)
Δθ = Change in temperature (oC)
For the mass the solutions we used are 1g.dm-3 so we use 25g and the specific heat capacity for the solutions is 4.2 J.deg-1.g-1

So we get

ΔH = 25g x 5oC x 4.2J.deg-1.g-1

ΔH = -525J (it is negative due to it being an exothermic reaction)

Now we need to transfer this into kJ.mol-1 for this we first divide the answer by 1000 to get it into kJ

ΔH = -0.525kJ

We used 0.025 mols so in order to get this per mol we need to times it by 40

ΔH = -21kJ.mol-1

Using this method you will obtain 2 values one for copper sulphate solution and one for lead nitrate solution.

In the reactivity series zinc and lead are closer together than zinc and copper. Using the 2 values that you obtain you will be able to test the prediction that the enthalpy change is relative to the distance of the 2 metals in the series.

Presumably the bigger distance of the 2 metals in the series the higher the enthalpy change will be.

In this experiment one main way in which we have tried to minimise our errors is by using a good
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