Question

A disbasic acid containing `C, H`, and `O` was found to contain `C = 26.7%` and `H=2.2%`. The vapor density of diethyl ester was found to be `73`. What is the molecular formula of the acid?
A. `C_2H_2O_4`
B. `C_4H_4O_4`
C. `C_3H_3O_4`
D. none of the these

Answer 1

Correct Answer - A

As it is a dibasic acid , it must contain two - COOH groups.
`therefore` Possible molecular formula
`(CHO_(2))_(2)=C_2H_(2)O_(4)`
`{:(COOH" "COOC_(2)H_(5)),(|" "+" "underset(-2H_(2)O)overset(2C_(2)H_(5)OH)to" "|),(COOH" "COOC_(2)H_(5)),("Dicarboxylic acid Diethyl ester"):}`
Mol .Mass of ester `= 6xx 12 + 4 xx 16 + 10` = 146
`therefore Mol.vapour density =("Mol.Mass ")/(2)`
`=146/2=73`
`therefore " Molecular formula fo ester "=(COOH)_(2)`