Question

The 0.2 g of anhydrous organic acid gave on combustion 0.04 g of water and 0.195 g of $C{O}_2$. The acid is a dibasic acid and 0.5 g of its silver salt leaves on ignition 0.355 g of silver. The empirical weight of the compound is

• A. 90
• B. 100
• C. 10
• D. 45

Answer 1

Answer: (D)

% of carbon $=\frac{12}{44}\times \frac{0.195}{0.2}\times 100=26.6$
% of hydrogen $=\frac{2}{18}\times \frac{0.04}{0.2}\times 100=2.22$
% of oxygen $=100-\left(26.6+2.22\right)=71.18$

Element	C	H	O
%	26.6	2.22	71.18
%/At. wt.	$\frac{26.6}{12}=2.22$	$\frac{2.22}{1}=2.22$	$\frac{71.18}{16}=4.44$
Relative number of atoms	$\frac{2.22}{2.22}=1$	$\frac{2.22}{2.22}=1$	$\frac{4.44}{2.22}=2$

Hence, empirical formula $=CH{O}_2$
Hence, empirical weight $=12+1+32=45$