Question

A monobasic organic acid gave on combustion the following % compositions: $C:39.9$%, $H=6.69$%. Also $0.2565$ g of silver salt of acid gave on ignition $0.1659$ g of $Ag$. Calculate the molecular formula of an acid.

• A. $C{H}_{3}COOH$
• B. $C{H}_{3}CHO$
• C. $C{H}_{3}COC{H}_3$
• D. None of the above

Answer 1

The correct option is A $C{H}_{3}COOH$

Question approach;

in question he is asking about the organic acid and from the options given below we have only one acid i.e., acetic acid; so we left with two options, either A or D,

given, C% = 39.9% and H% = 6.69%

molecular weight of acetic acid = 60

so, the percentage of carbon can be calculated as,

% of C= $\frac{massofcarbon}{molecularweight}\times 100$

% of C= $\frac{24}{60}\times 100$ = 40%

% of H= $\frac{4}{60}\times 100$= 6.69%

Hence, the correct answer is $C{H}_{3}COOH$