Complex A has a composition of H12O6Cl3Cr. If the complex on treatment with conc. H2SO4 loses 13.5 % of its original mass, the correct molecular formula of A is[Given : atomic mass of Cr = 52 amu and Cl = 35 amu]

M.wt of  H12O6Cℓ3Cr=265%  loss is 13.5. So amount of water lost per 1 mol ≈36. This is equal to 2 moles of water. The number of  H2O molecules lost should present in outer sphere of the hydrate isomer. So the correct formula of compound is CrH2O4Cℓ2Cℓ.2H2O