Enthalpy Change for Reaction of Anhydrous Copper (II) Sulfate with Water

Laboratory Report 1
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Laboratory Report 2
ABSTRACT
In a thermochemical equation, it is important to note state symbols (solid, liquid or gas)
because the enthalpy change, ∆H depends on the phase of the substances. In some cases, it is
very difficult to determine the enthalpy changes for reactions through experiment like in
situations where the reaction is too slow or too fast or by-products are formed. In such situation,
Hess's law is applied. When anhydrous copper (II) sulfate is added to water then there will be a
reaction which involves the physical change as the anhydrous copper (II) sulfate (white in
colour) changes to hydrated copper (II) sulfate (blue in colour). And during that reaction there
will be change in temperature. There will increase in temperature as this reaction takes place
therefore the reaction is an exothermic reaction. When water is added to the anhydrous copper
(II) sulfate, the water molecule will hence chemically combine with the anhydrous copper (II)
sulfate to form a hydrated copper (II) sulfate having water molecules chemically combined as
seen below;
CuSO4 (s) + 5H2O (l) CuSO4.5H2O (s)

Laboratory Report 3
AIM OF THE PRACTICAL
To obtain the enthalpy change for the reaction when anhydrous copper (ii) sulfate is
reacted with water to get hydrated copper (ii) sulfate, this enthalpy cannot be measured directly.
INTRODUCTION
Enthalpy change is the amount of energy which is absorbed or evolved during chemical reaction
at a constant pressure. An easier way to obtain the change in enthalpy for a chemical reaction is
to take change in the temperature as a result of the same reaction.
ΔH = m cp ΔT................................................................................................ 1
ΔH = the enthalpy of the reaction
ΔT = change in temperature
Cp = the heat capacity of the substance which changes temperature
m = the mass of the sample which changes the temperature
In a thermochemical equation, it is important to note state symbols (solid, liquid or gas)
because the enthalpy change, ∆H, depends on the phase of the substances. In some cases, it is
very difficult to determine the enthalpy changes for reactions through experiment like in
situations where the reaction is too slow or too fast or by-products are formed (Cemic, 2015). In
such situation, Hess's law is applied. The Law states that the enthalpy change for a chemical
reaction is independent of the route taken. This implies that the change in enthalpy for the overall
reaction will be identical irrespective of how many steps are covered (Dahm, 2014). This law can
be illustrated as below.

Laboratory Report 4
The enthalpy change moving from point A to B can be obtained by adding the values of the
values of the enthalpy changes for the reaction A to X, X to Y and Y to B (Sato, 2014)..
∆Hr= ∆ H 1 + ∆ H 2 +∆ H 3
Hess's Law using enthalpy of formation data can be illustrated as below
DH[reaction] = sum DHfo[products] - sum DHfo[reactants]