Chemistry - Stoichiometry Question with Solution | TestHub

ChemistryStoichiometryBasic Methods of Calculations (POAC, LR)Medium2 minQB

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A mixture of $NaNO_{2}$ and $NaNO_{3}$ is weighed ( 1.0 g ) and dissolved in water. It is reacted with an excess of $NH_{4}$ Cl and heated. The evolved gas occupies 224 mL at STP. What is the mass percentage of $NaNO_{2}$ in the mixture? (Molar masses: $NaNO_{2} = 69, NaNO_{3} = 85$ )

Options:

Answer:

Solution:

Concepts: Stoichiometry, reaction of $NH_{4}^{+}$ with $NO_{2}^{-}$ (comproportionation).

Solution:

1. ${NH}_{4}^{+} + {NO}_{2}^{-} \overset{∆}{\to} N_{2} + 2 H_{2} O$

2.NO₃^- does not react with NH₄Cl to give N₂ under these conditions.

3. Moles of N₂ = $224/22400 = 0.01 m o l$ .

4. Moles of NaNO₂ = $0.01 m o l$ .

5. Mass of NaNO₂ = $0.01 \times 69 = 0.69 g$ .

6. % NaNO₂ $= \frac{0.69}{1.0} \times 100 = 69%$

Correct Answer: 69%

Stream:JEESubject:ChemistryTopic:StoichiometrySubtopic:Basic Methods of Calculations (POAC, LR)

⏱ 2mℹ️ Source: QB

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