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Difficulty: HardDefinitions and Classical vs Modern Concepts of Redox

In chemical analysis, oxidation-reduction reactions are interpreted using either classical transfer principles (oxygen/hydrogen) or modern electronic and oxidation-state theories. Match each chemical transformation on the left with the specific classical or modern redox definition concept on the right that governs it.

  • The conversion of ammonia to nitrogen gas in 2NH3(g)+3CuO(s)→N2(g)+3Cu(s)+3H2O(l)2\text{NH}_{3(g)} + 3\text{CuO}_{(s)} \rightarrow \text{N}_{2(g)} + 3\text{Cu}_{(s)} + 3\text{H}_2\text{O}_{(l)}Classical oxidation defined as the removal of hydrogen from a compound
  • The half-reaction process Mg(s)→Mg(aq)2++2e−\text{Mg}_{(s)} \rightarrow \text{Mg}^{2+}_{(aq)} + 2e^-Modern oxidation defined as the loss of electrons by a chemical species
  • The change in manganese species from MnO4(aq)−\text{MnO}_{4(aq)}^- to Mn(aq)2+\text{Mn}_{(aq)}^{2+}Modern reduction defined as a decrease in the oxidation state of an element
  • The catalytic conversion of ethene to ethane via C2H4(g)+H2(g)→C2H6(g)\text{C}_2\text{H}_{4(g)} + \text{H}_{2(g)} \rightarrow \text{C}_2\text{H}_{6(g)}Classical reduction defined as the addition of hydrogen to a substance

Answer

The conversion of ammonia to nitrogen gas matches classical oxidation via hydrogen removal. The oxidation of magnesium metal to magnesium ions matches modern electronic oxidation via electron loss. The change of permanganate ion to manganese(II) ion matches modern reduction via a decrease in oxidation state from +7 to +2. The conversion of ethene to ethane matches classical reduction via hydrogen addition.
Each pair correctly matches a specific chemical transformation with its governing classical or modern redox rule. The removal of hydrogen from ammonia is classical oxidation. The loss of electrons from magnesium metal is modern electronic oxidation. The reduction in oxidation number of manganese from +7 to +2 is modern reduction. The addition of hydrogen to ethene is classical reduction.

Step-by-Step Solution

1
Analyze the conversion of 2NH32\text{NH}_3 to N2\text{N}_2
Ammonia loses hydrogen atoms during the reaction.
According to classical redox concepts, the removal of hydrogen from a compound constitutes oxidation.
2
Analyze the half-reaction Mg→Mg2++2e−\text{Mg} \rightarrow \text{Mg}^{2+} + 2e^-
Magnesium loses two electrons.
Under modern electronic theory, oxidation is defined as electron loss (OIL - Oxidation Is Loss).
3
Analyze the reduction of MnO4−\text{MnO}_4^- to Mn2+\text{Mn}^{2+}
Manganese's oxidation state drops from +7+7 to +2+2.
According to modern oxidation number conventions, a drop/decrease in oxidation number represents reduction.
4
Analyze the hydrogenation of ethene C2H4+H2→C2H6\text{C}_2\text{H}_4 + \text{H}_2 \rightarrow \text{C}_2\text{H}_6
Hydrogen is added across the carbon-carbon double bond.
Classical redox principles define reduction as the gain or addition of hydrogen.

Key Concept

Classical vs Modern Concepts of Redox
Estimated Time:2m 0s
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Topics

Definitions and Classical vs Modern Concepts of Redox

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