Question

A $10mg$ effervescent tablet contianing sodium bicarbonate and oxalic acid releases $0.25ml$ of $C{O}_2$ at $T=298.15K$ and $p=1$ bar. If molar volume of $C{O}_2$ is $25.0L$ under such condition, what is the percentage of sodium bicarbonate in each tablet? [Molar mass of $NaHC{O}_3=84gmo{l}^{-1}$ ]

• A. 16.8
• B. 8.4
• C. 0.84
• D. 33.6

Answer 1

Answer: (B)

$2NaHC{O}_3+H_2{C}_2{O}_4\to N{a}_2{C}_2{O}_4+2C{O}_2+2H_{2}O$
Here, number of moles of $C{O}_2=\frac{0.25\times 10^{-3}}{25.9}\approx 10^{-5}$
Now, one mole of $C{O}_2$ is produced by one mole of $NaHCO{C}_3$.
$\therefore$ the number of moles of $NaHC{O}_3$ in the given reaction $=$ number of moles of $C{O}_2=10^{-5}$
Now, the weight of $NaHC{O}_3=10^{-5}\times 84$
$=84\times 10^{-5}g$
$\therefore \%$ Mass $=\frac{84\times 10^{-5}}{10\times 10^{-3}}\times 100$
$=8.4\%$