The correct option is C +3
According to given conditions, we have
Sn2+⟶Sn4++2e−;increase in O.N=2
Ce4++ne−⟶Ce(4−n); decrease in O.N=n
On balancing, we get
nSn2++2Ce4+⟶nSn4++2Ce(4−n)
Given,
Millimoles of Sn2+=100×0.1=10
Millimoles of Ce4+=50×0.4=20
At equivalent point, number of equivalents of both reactant and product are same.
Therefore, n2=1020
or, n=1
Thus, oxidation state of cerium in the reduced product (Ce(4−1)=Ce3+)=+3.