Answer to Calculation Two

The Correct answer was 2

The calculations make use of the equations:
ΔG° = RTlnβ
ΔG° = 2.303RTlog10β
ΔG° = ΔH° - TΔS°

The answers again were:

  1. -190, -214 JK-1mol-1
  2. 1.9, 25.2 JK-1mol-1
  3. -5.3, -4.1 JK-1mol-1
  4. 23, 300 JK-1mol-1
First it is necessary to calculate the ΔG values from the given formation constants and temperature 25C = 298K.

For the ammonia complex, ΔG = -8.314 * 298 * 2.303 * 5.01 kJmol-1, that is -28.6 kJmol-1.

For the 1,2-diaminoethane complex, ΔG= -8.314 * 298 * 2.303 * 6.15 kJmol-1 which corresponds to -35.1 kJmol-1.

This makes use of the relation between Ln and log10 such that ln(x) = 2.303 log10 (x).

Then using the second relationship above, ΔS can be found.

            ΔH - ΔG
    ΔS = --------------
               T
For the ammonia complex this gives 1.9 JK-1mol-1
and for the 1,2-diaminoethane complex 25.2 JK-1mol-1,
which are the values given as answer 2.
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