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Ch.5 - Thermochemistry
Chapter 5, Problem 121a2

Consider the following unbalanced oxidation-reduction reactions in aqueous solution:
Ag+(aq) + Li(s) → Ag(s) + Li+(aq)
Fe(s) + Na+(aq) → Fe2+(aq) + Na(s)
K(s) + H2O(l) → KOH(aq) + H2(g)
(a) Balance second reaction.

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1
Identify the oxidation and reduction processes in the reaction: \( \text{Fe(s)} + \text{Na}^+\text{(aq)} \rightarrow \text{Fe}^{2+}\text{(aq)} + \text{Na(s)} \).
Determine the oxidation states of each element in the reaction. Fe goes from 0 to +2, and Na goes from +1 to 0.
Write the half-reactions for oxidation and reduction. Oxidation: \( \text{Fe(s)} \rightarrow \text{Fe}^{2+}\text{(aq)} + 2e^- \). Reduction: \( \text{Na}^+\text{(aq)} + e^- \rightarrow \text{Na(s)} \).
Balance the electrons in the half-reactions. Multiply the reduction half-reaction by 2 to balance the electrons: \( 2\text{Na}^+\text{(aq)} + 2e^- \rightarrow 2\text{Na(s)} \).
Combine the balanced half-reactions to form the balanced overall reaction: \( \text{Fe(s)} + 2\text{Na}^+\text{(aq)} \rightarrow \text{Fe}^{2+}\text{(aq)} + 2\text{Na(s)} \).

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Key Concepts

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

Oxidation-Reduction Reactions

Oxidation-reduction (redox) reactions involve the transfer of electrons between species, resulting in changes in oxidation states. In these reactions, one species is oxidized (loses electrons) while another is reduced (gains electrons). Understanding the roles of oxidizing and reducing agents is crucial for balancing redox reactions.
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Oxidation and Reduction Reactions

Balancing Redox Reactions

Balancing redox reactions requires ensuring that the number of atoms and the total charge are equal on both sides of the equation. This often involves identifying half-reactions for oxidation and reduction, balancing them separately, and then combining them to form a balanced overall equation. The use of coefficients is essential to achieve this balance.
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Balancing Basic Redox Reactions

Aqueous Solutions and Ionic Compounds

In aqueous solutions, ionic compounds dissociate into their constituent ions. Understanding how these ions interact in solution is vital for predicting the products of reactions. For example, in the given reactions, recognizing the states of matter (solid, liquid, aqueous) helps in determining the solubility and reactivity of the compounds involved.
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Related Practice
Textbook Question

Suppose an Olympic diver who weighs 52.0 kg executes a straight dive from a 10-m platform. At the apex of the dive, the diver is 10.8 m above the surface of the water. (a) What is the potential energy of the diver at the apex of the dive, relative to the surface of the water?

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Textbook Question

Suppose an Olympic diver who weighs 52.0 kg executes a straight dive from a 10-m platform. At the apex of the dive, the diver is 10.8 m above the surface of the water. (b) Assuming that all the potential energy of the diver is converted into kinetic energy at the surface of the water, at what speed, in m/s, will the diver enter the water?

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Textbook Question

Consider the following unbalanced oxidation-reduction reactions in aqueous solution:

Ag+(aq) + Li(s) → Ag(s) + Li+(aq)

Fe(s) + Na+(aq) → Fe2+(aq) + Na(s)

K(s) + H2O(l) → KOH(aq) + H2(g)

(a) Balance third reaction.

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views
Textbook Question

Consider the following unbalanced oxidation-reduction reactions in aqueous solution:

Ag+(aq) + Li(s) → Ag(s) + Li+(aq)

Fe(s) + Na+(aq) → Fe2+(aq) + Na(s)

K(s) + H2O(l) → KOH(aq) + H2(g)

(d) Use the activity series to predict which of these reactions should occur. (Section 4.4) Are these results in accord with your conclusion in part (c) of this problem?

Textbook Question
Consider the following acid-neutralization reactions involvingthe strong base NaOH(aq):HNO31aq2 + NaOH1aq2¡NaNO31aq2 + H2O1l2HCl1aq2 + NaOH1aq2¡NaCl1aq2 + H2O1l2NH4+1aq2 + NaOH1aq2¡NH31aq2 + Na+1aq2 + H2O1l2(d) In the third equation NH4+1aq2 is acting as an acid. Basedon the value of H° for this reaction, do you think it is astrong or a weak acid? Explain.
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