Page 23 - Lab Manual & Project class 12

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(v) Note down the temperature attained by the solution after
the addition of copper sulphate. Let this be t' °C. Calculate
2
the enthalpy of dissolution of copper sulphate as follows:
Total mass of the solution = Mass of Solvent + Mass of Solute
= (100 + W) g
1
–1
(Assuming density of water to be equal to 1 gL at the
experimental temperature)
Note : To find out enthalpy
Change in temperature = (t' - t' ) °C
2 1 change for the dissolution
Enthalpy change of the calorimeter (beaker) = W (t' - t' ) of potassium nitrate, use
2 1
where, W = Calorimeter constant potassium nitrate in place
of copper sulphate in this
Enthalpy change of solution = [(100 + W ) (t' - t' )] 4.184 J
1 2 1 experiment.
for (t' - t' ) °C rise in temperature
2 1
Total enthalpy change
of the Calorimeter = [W (t' - t' ) + (100 + W) (t' – t' )] × 4.184 J
2 1 1 2 1
(beaker) and solution

Heat liberated
on dissolution [W (t' - t' ) + (100 + W ) (t' - t' )] × 4.184 J
2
1
1
1
2
=
of 1 g copper W
1
sulphate Maxbrain Chemistry
Since 1 mol of copper sulphate weighs 249.5 g. Therefore,
[W(t' – t' ) + (100 + W )(t' – t' )] 4.184 –1
∆ H of CuSO .5H O = 249.5 × 2 1 1 2 1 J mol
Sol 4 2
W
1

Enthalpy change in the dissolution of copper sulphate/potassium
–1
nitrate is _______ Jmol .



(a) To record the temperature of water, use a thermometer with 0.1°C graduation.
(b) In the determination of calorimeter constant record the temperature of hot water
just before mixing.
(c) Avoid using very large amounts of copper sulphate/potassium nitrate.
(d) Stir the solution well to dissolve the solid and record the temperature. Avoid too
much stirring, it may produce heat due to friction.
(e) Weigh copper sulphate carefully as it is hygroscopic in nature.
(f) Use cotton wool to create insulation between the two beakers.



24-04-2018