A 10 g effervescent tablet containing sodium bicarbonate and oxalic acid releases 25 mL of $\mathrm{CO}_{2}$ at $\mathrm{T}=298.15 \mathrm{~K}$ and $\mathrm{p}=1$ bar. If molar volume of $\mathrm{CO}_{2}$ is 25.0 L under such condition, what is the percentage of sodium bicarbonate in each tablet? [Molar mass of $\mathrm{NaHCO}_{3}=84 \mathrm{~g} \mathrm{~mol}^{-1}$ ]

JEE Main · 2019 · 11 Jan 2019 · Shift 1 · Some Basic Concepts of Chemistry

A 10 g effervescent tablet containing sodium bicarbonate and oxalic acid releases 25 mL of

CO_{2}

T = 298.15 K

and

p = 1

bar. If molar volume of

CO_{2}

is 25.0 L under such condition, what is the percentage of sodium bicarbonate in each tablet? [Molar mass of

NaHCO_{3} = 84 g mol^{- 1}

]

Answer: (A)

Each mole of

NaHCO X_{3}

consumed releases one mole of

CO X_{2}

. The gas evolved,

25 mL

, divided by the molar volume of

25.0 L

gives

n_{CO X_{2}} = \frac{25 \times 1 0 ^{- 3}}{25.0} = 1 0^{- 3} mol

, so

1 0^{- 3}

mol of

NaHCO X_{3}

reacted, a mass of

1 0^{- 3} \times 84 = 0.084 g

. As a fraction of the

10 g

tablet this is

\frac{0.084}{10} \times 100 = 0.84%

JEE Main · 2019 · 11 Jan 2019 · Shift 1 · Single correct option