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Difficulty: Very hardPhysical and Chemical Properties of Acids and Bases

Equal masses of zinc granules are added separately to beaker P containing 100 cm3100\text{ cm}^3 of 1.0 mol dm−3 H2SO4(aq)1.0\text{ mol dm}^{-3}\text{ H}_2\text{SO}_4(aq) and beaker Q containing 100 cm3100\text{ cm}^3 of 1.0 mol dm−3 HNO3(aq)1.0\text{ mol dm}^{-3}\text{ HNO}_3(aq) at room temperature. Which of the following statements correctly identifies and explains the primary gaseous product liberated in each beaker?

  1. Beaker P liberates hydrogen gas through typical acid-metal displacement, whereas beaker Q liberates oxides of nitrogen because trioxonitrate(V) acid acts as a strong oxidizing agent.Answer
  2. B
    Both beakers liberate equal volumes of hydrogen gas because both acids are strong electrolytes that fully ionize in aqueous solution.
  3. C
    Beaker Q liberates twice the volume of hydrogen gas produced in beaker P because trioxonitrate(V) acid undergoes complete reduction to hydrogen ions.
  4. D
    Beaker P liberates sulfur(IV) oxide gas due to the dehydrating action of tetraoxosulfate(VI) acid, while beaker Q liberates hydrogen gas.

Answer

Beaker P liberates hydrogen gas through typical acid-metal displacement, whereas beaker Q liberates oxides of nitrogen because trioxonitrate(V) acid acts as a strong oxidizing agent.
Dilute tetraoxosulfate(VI) acid (H2SO4H_2SO_4) reacts with active metals such as zinc via standard single-replacement to evolve hydrogen gas (H2H_2). Conversely, trioxonitrate(V) acid (HNO3HNO_3) is a strong oxidizing acid; the nitrate ions (NO3−NO_3^-) are preferentially reduced to oxides of nitrogen rather than hydrogen ions being reduced to hydrogen gas.

Step-by-Step Solution

1
Analyze the chemical reaction between zinc and dilute tetraoxosulfate(VI) acid in beaker P.
Zinc displaces hydrogen ions from dilute H2SO4H_2SO_4 to yield zinc tetraoxosulfate(VI) and hydrogen gas: Zn(s)+H2SO4(aq)→ZnSO4(aq)+H2(g)\text{Zn}(s) + \text{H}_2\text{SO}_4(aq) \rightarrow \text{ZnSO}_4(aq) + \text{H}_2(g).
Dilute tetraoxosulfate(VI) acid exhibits standard acid behavior with reactive metals above hydrogen in the electrochemical series.
2
Analyze the chemical reaction between zinc and dilute trioxonitrate(V) acid in beaker Q.
Nitrate ions (NO3−NO_3^-) act as powerful oxidizing agents, undergoing reduction to form nitrogen oxides (such as N2ON_2O, NONO, or NO2NO_2) instead of liberating hydrogen gas.
Trioxonitrate(V) acid (HNO3HNO_3) is a strong oxidizing acid, so hydrogen ions are not reduced to H2(g)H_2(g) during reaction with metals.
3
Synthesize the observations from both beakers to select the correct explanation.
Beaker P produces H2(g)H_2(g) while beaker Q produces oxides of nitrogen.
The distinct chemical property of HNO3HNO_3 as an oxidizing acid alters the gaseous product compared to typical mineral acids.

Key Concept

Oxidizing property of trioxonitrate(V) acid versus typical acid-metal displacement reactions
Estimated Time:2m 0s
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Topics

Physical and Chemical Properties of Acids and Bases

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