Chemistry - Mole Concept Question with Solution | TestHub

To find $p+q$, we first determine the molecular weight of the amide.

Given 9.9 g amide evolves 1.7 g NH₃.

Moles of NH₃ = $1.7g/17g/mol=0.1mol$.

Since the amide is $C_4{H}_5{N}_a{O}_b$ and it evolves 'a' moles of NH₃, then $a=0.1mol$.

This implies that 9.9 g of amide contains 0.1 mol of nitrogen.

Mass of N = $0.1mol\times 14g/mol=1.4g$.

Percentage of N = $(1.4g/9.9g)\times 100\%=14.14\%$.

Given percentage of O = $33.33\%$.

Ratio of N and O atoms (p:q) is given by the ratio of (percentage/atomic mass):

$p:q=(14.14/14):(33.33/16)=1.01:2.08\approx 1:2$.

So, $p=1$ and $q=2$.

Therefore, $p+q=1+2=3$.