Question

2.0 g mixture of sodium carbonate and sodium bicarbonate on heating to constant mass gave 224 mL of $C{O}_2$ at NTP. The % mass of sodium bicarbonate in the mixture is:

• A. 50
• B. 54
• C. 80
• D. 84

Answer 1

The correct option is A 50

Sodium bicarbonate decomposes in

the following manner.

$2NaHC{O}_3\to N{a}_{2}C{O}_3+H_{2}O+C{O}_2$

Sodium Carbonate is stable and

doesn't dissociate upon normal

heating.

Vol. of $C{O}_2=224ml$

$22.4Ltr=1mole$

So moles of $C{O}_2=0.224/22.4=0.01mole$

$0.01mole=44\times 0.01g=0.44g$

1 mole $C{O}_2$ is procured by 2 mole $NaHC{O}_3$

$\therefore$ Moles of $NaHC{O}_3=2\times 0.01=0.02$

$=0.02\times 84=1.689$

$\%$ age $=\frac{mass}{Totalmass}\times 100=\frac{1.68}{2}\times 100=84\%$