Balance the redox equation by the ion-electron method: Bi(OH)_3+SnO_2^{2-} to SnO_3^{2-}+ Bi in...


Balance the redox equation by the ion-electron method: {eq}\displaystyle \rm Bi(OH)_3+SnO_2^{2-} \to SnO_3^{2-}+ Bi {/eq} in basic solution.

Half-Ion Reaction:

The Half-Ion Reaction method is a method that we use to derive complete chemical equations of reactions for either acidic or basic medium. For the case of a basic medium, we use the species {eq}\rm OH^- {/eq} and {eq}\rm H_2O {/eq} to balance the reactions.

Answer and Explanation: 1

Let's first deduce the half-reaction for the oxidation.

{eq}\rm SnO_2^{2-}\to SnO_3^{2-} {/eq}

Balance the oxygen atoms using {eq}\rm H_2O {/eq}.

{eq}\rm SnO_2^{2-}+H_2O \to SnO_3^{2-} {/eq}

Balance the hydrogen atoms using {eq}\rm H^+ {/eq}.

{eq}\rm SnO_2^{2-}+H_2O \to SnO_3^{2-}+2H^+ {/eq}

Neutralize the hydrogen ions using {eq}\rm OH^- {/eq}:

{eq}\rm SnO_2^{2-}+H_2O ++2OH^- \to SnO_3^{2-}+2H^+ +2OH^-\\ \rm SnO_2^{2-}+H_2O ++2OH^- \to SnO_3^{2-}+2H_2O\\ {/eq}

Balance the charge:

{eq}\rm SnO_2^{2-}+H_2O ++2OH^- \to SnO_3^{2-}+2H_2O+2e^-\ \ \ (1) {/eq}

Let's repeat the same for the reduction reaction:

{eq}\rm Bi(OH)_3 \to Bi {/eq}

Here, we can just balance the reaction directly using {eq}\rm OH^- {/eq}:

{eq}\rm Bi(OH)_3 \to Bi+3OH^- {/eq}

Balance the charge:

{eq}\rm Bi(OH)_3 +3e^-\to Bi+3OH^-\ \ \ (2) {/eq}

Match the number of electrons in the half-reactions. The lowest common multiple for the number of electrons is 6.

Equation (1) multiplied by 3, we get:

{eq}\rm 3SnO_2^{2-}+3H_2O ++6OH^- \to 3SnO_3^{2-}+6H_2O+6e^-\ \ \ (3) {/eq}

Equation (2) multiplied by 2, we get:

{eq}\rm 2Bi(OH)_3 +6e^-\to 2Bi+6OH^-\ \ \ (4) {/eq}

Combine (3) and (4):

{eq}\begin{align*} \rm 3SnO_2^{2-}+3H_2O +6OH^- + 2Bi(OH)_3 +6e^- \to 3SnO_3^{2-}+6H_2O+6e^-+2Bi+6OH^-\\ \rm 3SnO_2^{2-} + 2Bi(OH)_3 \to 3SnO_3^{2-}+(6-3)H_2O+2Bi+(6-6)OH^-\\ \color{blue}{\boxed{\rm 3SnO_2^{2-} + 2Bi(OH)_3 \to 3SnO_3^{2-}+3H_2O+2Bi}} \end{align*} {/eq}

Learn more about this topic:

Balancing Redox Reactions and Identifying Oxidizing and Reducing Agents


Chapter 10 / Lesson 13

Learn about oxidizing and reducing agents, how to find them, and how to identify them in redox reactions. Learn about the different types of redox reactions and how to identify a redox reaction.

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