EXPERIMENTAL: AN INVESTIGATION INTO THE RELATIONSHIP BETWEEN THE ENERGY
RELEASED AND THE CONCENTRATION OF REACTANTS IN A DISPLACEMENT REACTION

Introduction
A displacement reaction is the chemical change which occurs when a more
reactive element displaces a less reactive element from its compound;

e.g.,       2Al(s) + 3CuSO4(aq) ——————————® Al2(SO4)3(aq) + 3Cu(s)

In this redox reaction, electrons are transferred from aluminium atoms
to copper(II) ions because aluminium is a better reducing agent (i.e.,
it is more easily oxidized); the redox half equations are:

                        2Al(s) ———————————® 2Al3+(aq) + 6e-

                3Cu2+(aq) + 6e- ———————————® 3Cu(s)

The aqueous sulfate ions are spectators, so the net ionic equation is:

             2Al(s) + 3Cu2+(aq) ———————————® 2Al3+(aq) + 3Cu(s)

[.. K > Ca > Na > Mg > Al > Zn > Fe > Sn > Pb > (H) > Cu > Hg > Ag ..]

For the reaction of aluminium with aqueous copper(II) sulfate, in the
presence of sodium chloride, you are required to investigate whether 
there is a direct relationship between the heat energy released and
the concentration of aqueous copper(II) sulfate; i.e., H = k × C ?

Notes
1.  Aqueous chloride ions facilitate the removal of the very thin oxide
layer which invariably covers aluminium: however, they do not catalyze
the reaction between (pure) aluminium and aqueous copper(II) sulfate.

2.  The heat energy released from a chemical reaction can be determined
by first measuring its temperature change, and then using the equation
H = m × c × DT, where: H is the heat energy released; m is the mass of 
substance; c is its specific heat capacity; and DT is the temperature
change.  [Assume that 1.00 cm³ of aqueous copper(II) sulfate has a mass
of 0.001 kg, and that its specific heat capacity is 4200 J kg-¹ K-¹.]

3.  You are provided with aluminium powder, aqueous copper(II) sulfate
(with an initial concentration of 0.300 mol dm-³), distilled water, and
sodium chloride.  In addition, you will need to use - within reason -
suitable apparatus.

4.  The proposed plan of your investigation should be presented in
detail; this plan may be modified as the investigation proceeds.

Dr. R. Peters                  Next                      Contents' List