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Topic: Electrochemistry  (Read 222 times)

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Offline INeedSerotonin

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Electrochemistry
« on: February 24, 2020, 08:58:06 AM »


Hello

I was given this exercise and some options, so I have to mark the correct one.

a) an aqueous solution of hypochlorite can oxidize ions Mn2+
b) an aqueous solution of H2O2 is a strong reducing agent
c) ozone leans strongly to giving out electrons in an aqueous solution
d) the addition of H2O2 to an aqueous solution--having dissolved oxygen--promotes the formation of gas ozone
e) permanganate, among other substances in the image, is the most powerful oxidizing agent

I thought that all I had to do was look at the image and see the respective voltages, right? So I just marked (a) right away, because 1.63 V > 1.51 V, and I got it right.

But the thing is, after reading (d), I'm not so sure anymore if that's all I had to do. Perhaps I just found the correct answer by serendipity, and I actually had to play a bit with the reactions?

Can you guys confirm it to me?

Thank you very much

Offline mjc123

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Re: Electrochemistry
« Reply #1 on: February 24, 2020, 11:27:41 AM »
How do you think d is different, if at all,from the other statements? What do you mean by "play with the reactions"?

Offline INeedSerotonin

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Re: Electrochemistry
« Reply #2 on: February 24, 2020, 12:08:08 PM »
How do you think d is different, if at all,from the other statements? What do you mean by "play with the reactions"?

I think it differs from the others because it mentions many components, and the components come from different reactions.

For example, it mentions H2O2, which appears in the second reaction; and dissolved oxygen and gas ozone, which appear in the first reaction.

So I thought that maybe I would have to manipulate the reactions so as to make the statement true, like inverting the first one (because it says "formation of gas ozone"), putting ozone on the right side, and adding both reactions to make one only reaction from these two components.

It's also a reaction in equilibrium, which confuses me. I'm not even sure inverting them has any meaning at all, since it's in an equilibrium.

Offline OuJej1

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Re: Electrochemistry
« Reply #3 on: February 24, 2020, 05:05:04 PM »
Hello,
it's wonderful to see that you've thoroughly thought about this problem. I would say that option D) is one of those "nonsense" answers in this specific case - as you said, it mixes two of these reactions. I believe that there's not enough information provided to be able to mark D) as correct answer.
Have a nice day

Offline mjc123

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Re: Electrochemistry
« Reply #4 on: February 25, 2020, 04:48:54 AM »
But a also mentions components from different reactions, and e implicitly compares them all.
Quote
So I thought that maybe I would have to manipulate the reactions so as to make the statement true, like inverting the first one (because it says "formation of gas ozone"), putting ozone on the right side, and adding both reactions to make one only reaction from these two components.
You're on the right lines here. What do you get if you subtract equation 1 from equation 2 (or if you prefer, turn it round and add it)? What would be the cell voltage for this reaction? Is statement d true?

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