The number of moles of KCl in 3 L of 3 M solution is
27
3
1
9
In 3M there will be 3 moles per litre therefore in 3 litres there will be 9 moles.
Coefficient of y in the term −y9 is
Oxidation number of N in (NH4)2SO4 is
Oxidation number of cobalt in K[Co(Co)4] is