When you electrolyse an aqueous solution of NaCl, the product formed at cathode is H2 gas (preferential discharging), but the product formed at anode is Cl2 gas.
There is another complication. The book is missing the fact whether chlorine or oxygen is evolved depends on the concentration of the salt. At low salt concentrations, oxygen will be formed and at ...
Very simplistic explanations (or rationalisations, rather):
To create a diatomic gas, you need to oxidise or reduce two ions in very close proximity. That requires a little extra energy/potential, which turns into heat once the two single atoms recombine.
There are more possible contributions. The extra "dipolar" charge on the ion by its deformed hydrate ...
Cr2+ which has d4 configuration gets converted to Cr3+ which has d3 has half-filled t2g orbital
Which makes it good reducing agent
while In case of Mn3+ which had d4 Configuration gets converted to Mn2+ which has d5 configuration giving it half –filled d-configuration has more stability which makes it good oxidising agent.
Also Cr2+ ...