Question

A 10 mg effervescent tablet contianing sodium bicarbonate and oxalic acid releases 0.25 ml of $C{O}_2$ at T = 298.15 K and p = 1 bar. If molar volume of $C{O}_2$ is 25.9L 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)

8.4

$2NaHC{O}_3+H_2{C}_2{O}_4\to N{a}_2{C}_2{O}_4+2C{O}_2+2H_{2}O$

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 $NaHC{O}_3$.

$\therefore$ 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$=\frac{84\times {10}^{-5}}{10\times {10}^{-3}}\times 100=8.4\%$

Hence, the correct option is $B$