Determine whether or not each redox reaction occurs spontaneously in the forward direction.
a. Ca²⁺(aq) + Zn(s) → Ca(s) + Zn²⁺(aq)
b. 2 Ag⁺(aq) + Ni(s) → 2 Ag(s) + Ni²⁺(aq)
c. Fe(s) + Mn²⁺(aq) → Fe²⁺(aq) + Mn(s)
d. 2 Al(s) + 3 Pb²⁺(aq) → 2 Al³⁺(aq) + 3 Pb(s)

Verified step by step guidance

Identify the oxidation and reduction half-reactions. In this case, silver ions (Ag+) are reduced to silver metal (Ag), and nickel metal (Ni) is oxidized to nickel ions (Ni2+).

Write the half-reactions separately. For reduction: Ag+ + e- → Ag. For oxidation: Ni → Ni2+ + 2e-.

Check the standard reduction potentials for each half-reaction. The standard reduction potential for Ag+ to Ag is +0.80 V, and for Ni to Ni2+ it is -0.25 V.

Calculate the standard cell potential (E°cell) for the reaction by subtracting the standard reduction potential of the anode (oxidation) from the cathode (reduction). E°cell = E°cathode - E°anode.

Determine the spontaneity of the reaction. If E°cell is positive, the reaction is spontaneous in the forward direction; if it is negative, the reaction is non-spontaneous.

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Key Concepts

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

Redox Reactions

Redox reactions, or reduction-oxidation reactions, involve the transfer of electrons between two species. In these reactions, one species is oxidized (loses electrons) while the other is reduced (gains electrons). Understanding the oxidation states of the elements involved is crucial for identifying which species undergo these changes.

Standard Electrode Potentials

Standard electrode potentials (E°) are measured values that indicate the tendency of a species to be reduced. Each half-reaction has a specific E° value, and the overall spontaneity of a redox reaction can be determined by calculating the cell potential (E°cell) using the formula E°cell = E°(reduction) - E°(oxidation). A positive E°cell indicates that the reaction is spontaneous in the forward direction.

Spontaneity of Reactions

The spontaneity of a reaction refers to its ability to occur without external intervention. In the context of redox reactions, spontaneity can be assessed through Gibbs free energy (ΔG). A negative ΔG corresponds to a spontaneous reaction, which can be related to the cell potential; specifically, ΔG = -nFE°cell, where n is the number of moles of electrons transferred and F is Faraday's constant.

Related Practice

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Determine whether or not each metal dissolves in 1 M HCl. For those metals that do dissolve, write a balanced redox reaction showing what happens when the metal dissolves. a. Al b. Ag c. Pb

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Which metal can be oxidized with an Sn²⁺ solution but not with an Fe²⁺ solution?

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