[blamendola25]

I am studying for a test next tuesday, and I am having trouble on a couple of questions. The questions are:

1. Which of the following compounds would you expect to have to undergo electrolysis to obtain free metals? explain your choice.

  a. KCl          b. Ag₂O   c. Fe₂O₃

2. Explain why corresponding phosphorus and arsenic compounds resemble each other more closely than they do nitrogen compounds.

I have asked the teacher for help, but all he does is makes it more confusing. Can anyone help?

[Arkcon]

1. Which of the following compounds would you expect to have to undergo electrolysis to obtain free metals? explain your choice.

  a. KCl          b. Ag₂O   c. Fe₂O₃

Sing it with me:  One of these things is not like the others, one of these things is totally different.

2. Explain why corresponding phosphorus and arsenic compounds resemble each other more closely than they do nitrogen compounds.

Look at the periodic table.  What is happening to phosphorus and arsenic, given their position?

I have asked the teacher for help, but all he does is makes it more confusing. Can anyone help?

What did he say?  It might have been more insightful, if you tried a bit harder.

[blamendola25]

I still can't figure out the first one. He said to use the reduction potentials to find out if the metal would be replaced in a single replacement reaction. I have tried setting up a single replacement reaction, but I can't find the reduction potential for the new compound anywhere. As for the second question, there a couple of things happening from nitrogen to Arsenic like decreasing ionization energy and decreasing electronegativity, but I don't know why the arsenic and phosphorus would resemble each other more than say nitrogen and phosphorus. Does that make sense?

[Borek]

This electrolysis question doesn't make much sense to me.

Reduction potentials are listed for dissolved substances, of the three substances given only one is soluble (and the presence of water definitely changes the situation). It is also possible to electrolyze melted substances - but at least one of the substances listed will decompose long before melting. So, no matter which way you look at the problem, each case is different and there is no single approach that will allow to treat each substance the same way. Under some assumptions metals can be recovered from all three substances, under some other assumptions they can't be recovered from neither.

[Arkcon]

- but at least one of the substances listed will decompose long before melting.

Decomposes into what?  And doesn't that answer the question -- Which one isn't obtained free by electrolysis?

[Borek]

Decomposes into what?  And doesn't that answer the question -- Which one isn't obtained free by electrolysis?

Then the hint about reduction potentials is off, as they are irrelevant.