What is a disproportionation reaction? Use the following...

What is a disproportionation reaction? Use the following reduction potentials $$ \begin{aligned} \mathrm{ClO}_{3}^{-} &+3 \mathrm{H}^{+}+2 \mathrm{e}^{-} \longrightarrow \mathrm{HClO}_{2}+\mathrm{H}_{2} \mathrm{O} & & \mathscr{E}^{\circ}=1.21 \mathrm{~V} \\ \mathrm{HClO}_{2}+2 \mathrm{H}^{+}+2 \mathrm{e}^{-} \longrightarrow \mathrm{HClO}+\mathrm{H}_{2} \mathrm{O} & & \mathscr{E}^{\circ}=1.65 \mathrm{~V} \end{aligned} $$ to predict whether $\mathrm{HClO}_{2}$ will disproportionate.

What is a disproportionation reaction? Use the following reduction potentials
$$
\begin{aligned}
\mathrm{ClO}_{3}^{-} &+3 \mathrm{H}^{+}+2 \mathrm{e}^{-} \longrightarrow \mathrm{HClO}_{2}+\mathrm{H}_{2} \mathrm{O} & & \mathscr{E}^{\circ}=1.21 \mathrm{~V} \\
\mathrm{HClO}_{2}+2 \mathrm{H}^{+}+2 \mathrm{e}^{-} \longrightarrow \mathrm{HClO}+\mathrm{H}_{2} \mathrm{O} & & \mathscr{E}^{\circ}=1.65 \mathrm{~V}
\end{aligned}
$$
to predict whether $\mathrm{HClO}_{2}$ will disproportionate.

Key Concepts

Half-Reaction Method in Redox Analysis

The half-reaction method involves breaking down a redox process into its constituent oxidation and reduction reactions. This approach allows for the separate consideration of the individual electron transfer steps, facilitating the evaluation of whether a certain species can both oxidize and reduce itself in a disproportionation reaction.

Electrochemical Cell and Reaction Spontaneity

The overall spontaneity of a redox reaction depends on the cell potential, which is calculated by combining the reduction potentials of the half-reactions. A positive overall cell potential indicates that the reaction, including disproportionation processes, is thermodynamically favorable.

Reduction Potential

Reduction potential indicates the tendency of a chemical species to gain electrons under standard conditions. It is a key parameter in determining the direction and spontaneity of redox reactions, with higher potentials corresponding to a greater tendency to be reduced.

Disproportionation Reaction

A disproportionation reaction is a type of redox reaction in which a single chemical species undergoes both oxidation and reduction, forming two different products. This means that the same element in one oxidation state is simultaneously converted into higher and lower oxidation states.

Transcript

00:03 So in this video we're going to talk about question 92 from chapter 20, which asks us, what is a disproportionation reaction? use the following reduction potentials to predict whether hcl2 will disproportionate.

00:15 So a disproportionation reaction is one where one species is both oxidized and reduced.

00:21 So you have a reactant that is oxidized into one product and reduced into a different product.

00:27 So we want to know whether or not hcl2 will disproportionate.

00:32 And we're given two half reactions and the way they're written here, they're both reduction half reactions because we're gaining electrons.

00:41 But for a redox reaction, we want to write one of these half reaction as an oxidation half reaction that can be coupled with a reduction half reaction.

00:52 So which one do we write as an oxidation half reaction? which one do we write in the opposite direction? so remember when we write these in the opposite direction, we flip the sign, on the reduction potential.

01:05 And we want the overall cell potential to be a positive number because that means that the way we've written the reaction, it will occur spontaneously.

01:16 So when we're picking which one we're going to flip directions, which one we're going to write as oxidation, we're going to pick the one with the lower reduction potential.

01:24 So we're going to take this first half reaction with the reduction potential of 1 .21 volts, and we're going to write it in the opposite direction.

01:31 So let's go ahead and do that.

01:32 So that gives us hcl2 plus h2o yields hclo3 minus plus three protons plus two electrons and then our other half reaction we haven't changed at all.

01:42 It's still written in the forward direction it's hcl2 plus 2h plus two electrons yields hclo plus h2o so we want to add these together so let's figure out what cancels so first what cancels is our two electrons then we have a water molecule on both sides of our reaction.

02:04 And then we have two protons in our reactants and three protons in our products.

02:09 So our two protons cancel out and we have just one proton in our products.

02:13 So the overall reaction that occurs spontaneously, because remember we were careful to add these together so that our resulting cell potential will be positive, the overall reaction is 2hclo2 yields hcl3 plus h plus hclo.

02:29 So this seems like it could be a disproportionation reaction.

02:33 We could have hclo2 being reduced or oxidized to either hcl3 or hclo.

02:40 But in order to determine that, we need to first define the oxidation states.

02:50 So first, let's do this for our first half reaction.

02:54 So we have hclo2.

02:58 We know that the oxidation state for hydrogen is plus one when it's bonded to other atoms.

03:04 And the oxidation state for oxygen is minus two...

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