A dibasic acid containing C, H and O was found to contain C = 26.7% and H = 2.2%. The vapour density of its diethyl ester was found to be 73. The molecular formula of the acid is

Vapour density of diethylester = 73Molecular weight of Diethylester = 146General Formula of an ester = RCOOR'General Formula of an ethylester = RCOOC2H5General Formula of an carboxylic acid = RCOOHDecrease in weight when an ester is ofConverted to Carboxylic acid = RCOOC2H5 - Weight of  C2H5 + weight  of  H= Wt of RCOOC2H5 - 29 + 1= Wt of RCOOC2H5 - 28But we have a diethyl ester of a dicarboxylic acidMolecular weight  of dicarboxylic acid = (Molecular weight  of diethyl ester) - 2(28)= 146 - 56= 90Given: E.F of dicarboxylic acid = CHO2EFW of dicarboxylic acid = 12 + 1 + 2(16) = 45MFW of dicarboxylic acid = 90MF = (EF)2MF = (CHO2)2MF = C2H2O4