Question 3.4:
Calculate the potential of hydrogen electrode in contact with a solution whose pH is 10.
Answer:
For hydrogen electrode, , it is given that pH = 10
∴[H+] = 10−10 M
Now, using Nernst equation:
=
= −0.0591 log 1010
= −0.591 V
Question 3.5:
Calculate the emf of the cell in which the following reaction takes place:
Given that = 1.05 V
Answer:
Applying Nernst equation we have:
= 1.05 − 0.02955 log 4 × 104
= 1.05 − 0.02955 (log 10000 + log 4)
= 1.05 − 0.02955 (4 + 0.6021)
= 0.914 V
Question 3.6:
The cell in which the following reactions occurs:
has
= 0.236 V at 298 K.
Calculate the standard Gibbs energy and the equilibrium constant of the cell reaction.
Answer:
Here, n = 2, T = 298 K
We know that:
= −2 × 96487 × 0.236
= −45541.864 J mol−1
= −45.54 kJ mol−1
Again, −2.303RT log Kc
= 7.981
∴Kc = Antilog (7.981)
= 9.57 × 107