Write a balanced half-reaction for the product that forms at each electrode in the aqueous electrolysis of the following salts: (a) \(\mathrm{LiF} ;\) (b) \(\mathrm{SnSO}_{4}\).

Short Answer

Expert verified
For LiF: At the cathode, \(2\text{H}_2\text{O} + 2e^- \rightarrow \text{H}_2 + 2\text{OH}^-\); At the anode, \(2\text{H}_2\text{O} \rightarrow \text{O}_2 + 4\text{H}^+ + 4e^-\).For SnSO4: At the cathode, \( \text{Sn}^{2+} + 2e^- \rightarrow \text{Sn}\); At the anode, \(2\text{H}_2\text{O} \rightarrow \text{O}_2 + 4\text{H}^+ + 4e^-\).

Step by step solution

01

Identify the cations and anions

Determine the cations and anions in each salt.(a) For \(\text{LiF}\), the cation is \(\text{Li}^+\) and the anion is \(\text{F}^-\).(b) For \(\text{SnSO}_4\), the cation is \(\text{Sn}^{2+}\) and the anion is \(\text{SO}_4^{2-}\).
02

Write the possible half-reactions for each cation in aqueous solution

Consider the reduction half-reactions for cations that may occur during electrolysis in an aqueous solution.(a) For \(\text{Li}^+\): \(\text{Li}^+ + e^- \rightarrow \text{Li} \)Note: In aqueous solutions, reduction is more likely to produce hydrogen gas. Thus, also consider \(2\text{H}_2\text{O} + 2e^- \rightarrow \text{H}_2 + 2\text{OH}^-\).(b) For \(\text{Sn}^{2+}\): \(\text{Sn}^{2+} + 2e^- \rightarrow \text{Sn} \).
03

Write the possible half-reactions for each anion in aqueous solution

Consider the oxidation half-reactions for anions that may occur during electrolysis in an aqueous solution.(a) For \(\text{F}^-\): \(2\text{F}^- \rightarrow \text{F}_2 + 2e^- \)Note: In aqueous solutions, oxidation is more likely to produce oxygen gas. Thus, also consider \(2\text{H}_2\text{O} \rightarrow \text{O}_2 + 4\text{H}^+ + 4e^-\).(b) For \(\text{SO}_4^{2-}\): There is no direct oxidation of \(\text{SO}_4^{2-}\), instead consider the oxidation of water: \(2\text{H}_2\text{O} \rightarrow \text{O}_2 + 4\text{H}^+ + 4e^-\).
04

Determine the preferred half-reactions in the aqueous solutions

Evaluate the likelihood of each half-reaction occurring during the electrolysis process.(a) At the cathode for \(\text{LiF}\): The reduction of water to produce hydrogen gas is more favorable:\(2\text{H}_2\text{O} + 2e^- \rightarrow \text{H}_2 + 2\text{OH}^-\).At the anode for \(\text{LiF}\): The oxidation of water to produce oxygen gas is more favorable:\(2\text{H}_2\text{O} \rightarrow \text{O}_2 + 4\text{H}^+ + 4e^-\).(b) At the cathode for \(\text{SnSO}_4\): The reduction of \(\text{Sn}^{2+}\) is the expected reaction:\(\text{Sn}^{2+} + 2e^- \rightarrow \text{Sn} \).At the anode for \(\text{SnSO}_4\): The oxidation of water to produce oxygen gas is the expected reaction:\(2\text{H}_2\text{O} \rightarrow \text{O}_2 + 4\text{H}^+ + 4e^-\).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Cation Reduction
Cation reduction is a core process in electrolysis, where positively charged ions gain electrons to form neutral atoms. This typically occurs at the cathode, the electrode where reduction occurs. For example, in the electrolysis of \text{SnSO}_4\, the cation \(\text{Sn}^{2+}\) undergoes reduction. The half-reaction is: \[\text{Sn}^{2+} + 2e^- \rightarrow \text{Sn} \]. Here, the tin ion gains two electrons to form solid tin metal. Understanding cation reduction helps us determine which substances will be reduced during electrolysis.
Anion Oxidation
Anion oxidation is another key component of electrolysis. This occurs at the anode, the electrode where oxidation happens. Positively charged species lose electrons here. For example, during the electrolysis of \text{LiF}\, the possible oxidation of fluoride anion is represented by \(2\text{F}^- \rightarrow \text{F}_2 + 2e^- \). However, in aqueous solutions, water is more likely to be oxidized, forming oxygen gas: \[2\text{H}_2\text{O} \rightarrow \text{O}_2 + 4\text{H}^+ + 4e^- \]. Recognizing this likelihood is crucial for predicting products in an electrolysis process.
Aqueous Solution Electrolysis
Aqueous solution electrolysis involves the breakdown of substances dissolved in water using an electric current. In such solutions, not only do the ions of the solute participate, but water molecules also play a significant role. For instance, in the electrolysis of \text{LiF}\, while one might initially consider the reduction of lithium ions and oxidation of fluoride ions, water is more likely to undergo reduction and oxidation, given its abundance: \[2\text{H}_2\text{O} + 2e^- \rightarrow \text{H}_2 + 2\text{OH}^- \] for reduction and \[2\text{H}_2\text{O} \rightarrow \text{O}_2 + 4\text{H}^+ + 4e^- \] for oxidation. This understanding helps in accurately predicting electrolysis products in aqueous solutions.
Balanced Chemical Reactions
Writing balanced chemical reactions is essential to describe electrolysis processes accurately. Balancing ensures that the same number of each type of atom appears on both the reactant and product sides of a reaction. For instance, the reduction half-reaction of \(\text{SnSO}_4\) is \(\text{Sn}^{2+} + 2e^- \rightarrow \text{Sn} \), and an oxidation half-reaction of water can be \[2\text{H}_2\text{O} \rightarrow \text{O}_2 + 4\text{H}^+ + 4e^- \]. Ensuring these are balanced helps in understanding the conservation of mass and charge in chemical processes, which is fundamental for solving electrolysis problems.

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