pH of 0.5 M Ba(CN)2 solution (pKb of CN−=9.30) is :
8.35
3.35
9.35
9.50
[CN−]=2×0.5=1.0MpH=12(pKw+pKa+log[CN−])=12[14+(14−pKb)+log 1]=12[28−9.30]=9.35