Question

The percentage by weight of:
a] C in carbon dioxide
b] Na in sodium carbonate
c] AI in aluminium nitride.

are $27\%$, $43.4\%$, $65.85\%$ respectively
[C=12, O=16, H=1,Na=23, AI=27, N=14]

• A. True
• B. False

Answer 1

The correct option is A True

Solution:- (A) True

As we know that,

$\text{percentage by weight}=\frac{\text{weight}}{\text{total weight}}\times 100$

Therefore,

(a)percentage by weight of $C$ in carbon dioxide-

Weight of carbon in $C{O}_2=12g$

Weight of $C{O}_2=44g$

$\therefore$ percentage by weight $=\frac{12}{44}\times 100=27.27\%\approx 27\%$

(b)percentage by weight of $Na$ in sodium carbonate-

Weight of sodium $=23g$

Weight of sodium in ${Na}_{2}C{O}_3=2\times 23=46g$

Weight of ${Na}_{2}C{O}_3=106g$

$\therefore$ percentage by weight $=\frac{46}{106}\times 100=43.4\%$

(c)percentage by weight of $Al$ in aluminium nitride-

Weight of aluminium in $AlN=27g$

Weight of $AlN=41g$

$\therefore$ percentage by weight $=\frac{27}{41}\times 100=65.85\%$

Hence the given statement is true.