25 mL of N15NaOH solution ≡25 mL of N15 oxalic acid solution
Mass of oxalic acid present in 25 mL of N15 oxalic acid solution
=N×E×V1000=1×(90+18x)×2515×2×1000
=(90+18x)1200g
Actually (90+18x)1200g oxalic acid is present in 16.68 mL solution.
250 mL of the solution contains oxalic acid
=(90+18x)×2501200×16.68=1.575(given)
or 90+18x=1.575×1200×16.68250=126
or 18x=126−90=36
x=2.