A 10 mg effervescent tablet releases 0.25 mL of CO_2 at T = 298.15 K and p = 1 bar. The molar volume of CO_2 under these conditions is 25.0 L. The tablet contains sodium bicarbonate (NaHCO_3, molar mass = 84 g mol^ -1 ). What is the percentage of NaHCO_3 in each tablet?

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EEJ MAIN Chemistry QUESTION #7521

Question 1

A 10 mg effervescent tablet releases 0.25 mL of CO$_2$ at $T = 298.15$ K and $p = 1$ bar. The molar volume of CO$_2$ under these conditions is 25.0 L. The tablet contains sodium bicarbonate (NaHCO$_3$, molar mass = 84 g mol$^{-1}$). What is the percentage of NaHCO$_3$ in each tablet?

0.84%
33.60%
16.80%
8.40%✔️

Correct Answer Explanation

Moles of CO$_2 = \dfrac{0.25 \times 10^{-3}\ \text{L}}{25.0\ \text{L mol}^{-1}} = 1.0 \times 10^{-5}\ \text{mol}$

Reaction: $\text{NaHCO}_3 + \text{H}^+ \to \text{Na}^+ + \text{H}_2\text{O} + \text{CO}_2$

Moles of NaHCO$_3 = 1.0 \times 10^{-5}\ \text{mol}$

Mass of NaHCO$_3 = 1.0 \times 10^{-5} \times 84 = 8.4 \times 10^{-4}\ \text{g} = 0.84\ \text{mg}$

$\% = \dfrac{0.84}{10} \times 100 = \mathbf{8.4\%}$

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