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Ch.4 - Reactions in Aqueous Solution
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Not the one you use?Change textbook
All textbooksBrown 14th EditionCh.4 - Reactions in Aqueous SolutionProblem 51b
Chapter 4, Problem 51b

Which element is oxidized, and which is reduced in the following reactions? (b) 3 Fe(NO3)2(aq) + 2 Al(s) → 3 Fe(s) + 2 Al(NO3)3(aq)

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Identify the oxidation states of each element in the reactants and products. For the reactants: In Fe(NO3)2, iron (Fe) typically has an oxidation state of +2 and each nitrate (NO3) group has an oxidation state of -1. Aluminum (Al) is in its elemental form, so its oxidation state is 0. For the products: In Fe, iron is in its elemental form, so its oxidation state is 0. In Al(NO3)3, aluminum has an oxidation state of +3 and each nitrate group still has an oxidation state of -1.
Compare the oxidation states of each element in the reactants and products to determine the changes. Iron (Fe) changes from +2 in Fe(NO3)2 to 0 in Fe, indicating a decrease in oxidation state, which is a gain of electrons (reduction). Aluminum (Al) changes from 0 in its elemental form to +3 in Al(NO3)3, indicating an increase in oxidation state, which is a loss of electrons (oxidation).
Conclude which element is oxidized and which is reduced based on the changes in oxidation states. Aluminum (Al) is oxidized as it loses electrons (increase in oxidation state from 0 to +3). Iron (Fe) is reduced as it gains electrons (decrease in oxidation state from +2 to 0).
Write the half-reactions for each process to further illustrate the changes. Oxidation half-reaction: Al(s) → Al^3+(aq) + 3e^-. Reduction half-reaction: Fe^2+(aq) + 2e^- → Fe(s).
Combine the half-reactions to check if the overall electron transfer is balanced, ensuring the number of electrons lost in oxidation equals the number of electrons gained in reduction.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Oxidation and Reduction

Oxidation and reduction are chemical processes that involve the transfer of electrons between substances. Oxidation refers to the loss of electrons, resulting in an increase in oxidation state, while reduction involves the gain of electrons, leading to a decrease in oxidation state. These processes always occur simultaneously in a redox reaction.
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Oxidation and Reduction Reactions

Oxidation States

Oxidation states (or oxidation numbers) are assigned to atoms in a compound to indicate their degree of oxidation or reduction. They help in identifying which elements are oxidized and reduced in a reaction. For example, in the reaction provided, determining the oxidation states of iron (Fe) and aluminum (Al) will clarify which element undergoes oxidation and which undergoes reduction.
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Half-Reactions

Half-reactions are a way to separate the oxidation and reduction processes in a redox reaction. Each half-reaction shows either the loss of electrons (oxidation) or the gain of electrons (reduction) for a specific species. By writing the half-reactions for the given reaction, one can easily identify the oxidized and reduced elements, facilitating a clearer understanding of the overall reaction.
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Related Practice
Textbook Question

Which of the following are redox reactions? For those that are, indicate which element is oxidized and which is reduced. For those that are not, indicate whether they are precipitation or neutralization reactions. (a) P4(s) + 10 HClO(aq) + 6 H2O(l) → 4 H3PO4(aq) + 10 HCl(aq) (b) Br2(l) + 2 K(s)→ 2 KBr(s) (c) CH3CH2OH(l) + 3 O2(g) → 3 H2O(l) + 2 CO2(g) (d) ZnCl2(aq) + 2 NaOH(aq) → Zn(OH)2(s) + 2 NaCl(aq)

Textbook Question

Determine the oxidation number for the indicated element in each of the following substances: (e) Pt in PtCl4 (f) O in OF2.

Textbook Question

Which element is oxidized, and which is reduced in the following reactions? (a) N2(g) + 3 H2(g) → 2 NH3(g)

Textbook Question

Which element is oxidized, and which is reduced in the following reactions? (c) Cl2(aq) + 2 NaI(aq) → I2(aq) + 2 NaCl(aq) (d) PbS(s) + 4 H2O2(aq) → PbSO4(s) + 4 H2O(l)

Textbook Question

Write balanced molecular and net ionic equations for the reactions of (a) manganese with dilute sulfuric acid (b) chromium with hydrobromic acid (c) tin with hydrochloric acid (d) aluminum with formic acid, HCOOH.

Textbook Question

Determine the oxidation number for the indicated element in each of the following substances: (f) Cl in NaClO4.