[vedderfan94]

(Original post by TheBigDog)
I think it's Cd(OH)2, but to be honest it could be either. Some say how can Cd be the weakest oxidising agent whe it can never be reduced, so it can never be an oxidising agent. At the same time you can say that makes it the weakest because it can't oxidise anything

Would have been much easier if AQA asked for the strongest. But then again, this is AQA we're talking about.

Cd(OH)2 is reduced though. The weakest oxidising agent is the strongest reducing agent, so it is oxidised. Cd(OH)2 can't be oxidised (not in this question anyway).

[Notsocleverstudent]

For the p4o10 question, is it not represented as P4O10 because its also known as an oxidentate molecule?

[Msd27]

(Original post by vedderfan94)
Cd(OH)2 is reduced though. The weakest oxidising agent is the strongest reducing agent, so it is oxidised. Cd(OH)2 can't be oxidised (not in this question anyway).

But its talking about an oxidising agent - i.e something that gains electrons Cd does not gain electrons CD(OH)2 does!

[vedderfan94]

(Original post by Msd27)
The oxidising agent is reduced, not oxidised

But the weakest oxidising agent is oxidised.

[ayseta]

(Original post by Newbie123)
Yeah, but if someone asked you to name the weakest swimming fish, you wouldn't answer "a dog", would you?

Cd can't be the answer because it doesn't get reduced - so it lacks something that all oxidising agents, by definition, have in common.

You're saying that Cd lacks something that oxidising agents have. The question is asking for the WEAKEST oxidising agent...

[tony_dolby]

(Original post by Matthew692692)
I'm still confused even after looking at that link!!

The key thing is to identify your oxidizing agents. These are things that are good at being reduced, so if the E values are written as reduction potentials (which according to IUPAC they should be), then the most +ve value will mean that the species gaining electrons is the best oxidizing agent (it likes to be reduced)

However, remember that E values are experimentally derived so even though we can calculate the feasibility of reactions using these, we can't just invent E values for reactions that don't occur under standard conditions such as Cd + e- goes to Cd-

[Newbie123]

(Original post by vedderfan94)
Cd(OH)2 is reduced though. The weakest oxidising agent is the strongest reducing agent, so it is oxidised. Cd(OH)2 can't be oxidised (not in this question anyway).

Cd is not an oxidising agent, therefore it's incorrect to say it's the weakest oxidising agent.

The question before that question asked you for the definition of an oxidising agent - which is, an electron acceptor.

Cd doesn't accept electrons.

[Msd27]

(Original post by Notsocleverstudent)
For the p4o10 question, is it not represented as P4O10 because its also known as an oxidentate molecule?

Think it is to do with the fact P2O5 is the empirical formula but P4O10 is the formula of the actual molecule that exists in nature (empirical formula gives you the simplest ratio of atoms of specific elements in a molecule/compound)

[vedderfan94]

(Original post by Msd27)
But its talking about an oxidising agent - i.e something that gains electrons Cd does not gain electrons CD(OH)2 does!

It's talking about the weakest oxidising agent. Why are so many people overlooking this key word?

[LeeM1]

(Original post by Newbie123)
Yeah, but if someone asked you to name the weakest swimming fish, you wouldn't answer "a dog", would you?

Cd can't be the answer because it doesn't get reduced - so it lacks something that all oxidising agents, by definition, have in common.

If something doesn't get reduced it is an awful oxidising agent!

[LookIt'sPete]

(Original post by Msd27)
But its talking about an oxidising agent - i.e something that gains electrons Cd does not gain electrons CD(OH)2 does!

(Original post by Newbie123)
Yeah, but if someone asked you to name the weakest swimming fish, you wouldn't answer "a dog", would you?

Cd can't be the answer because it doesn't get reduced - so it lacks something that all oxidising agents, by definition, have in common.

(Original post by SilverArch)
You did. You said - weakest oxidising agent= strongest reducing agent. That isn't the case, something won't be an oxidising agent and a reducing agent at the same in the same equation.

Cd(OH)2 is the weakest oxidising agent. When it reacts in the equation AQA gave, it can't be a reducing agent, because it won't lose any more electrons.

Cd is not an oxidising agent, it won't gain more electrons. But it is a strong reducing agent (strongest in the table) because it is the best at giving away it's electrons

I reckon if we put in enough energy, it is possible to get Cd to accept an electron in the same way that it is possible to get a H- ion and, with enough energy, a Cl+ ion.

Following this logic, even if Cd is not a standard oxidising agent, it is the weakest one on the list as it is the one that finds it most difficult to accept an electron.

[SilverArch]

(Original post by ayseta)
I didn't say it was?

Ok so if something is an oxidising agent, it will accept electrons right?

The Cd(OH)2 equation is showing the reduction process. It has a negative electrode potential, so the reaction that will happen is the oxidation one:

Cd(s) + 2OH- -> Cd(OH)2(s) + 2e-


This equation shows Cd getting oxidised (OILRIG - Oxidation is LOSS OF ELECTRONS) . Remember the definition of an oxidising agent - they ACCEPT ELECTRONS.

If Cd is getting oxidised (losing electrons) then it's going to be weakest at accepting them surely?

You did. You said - weakest oxidising agent= strongest reducing agent. That isn't the case, something won't be an oxidising agent and a reducing agent at the same in the same equation.

Cd(OH)2 is the weakest oxidising agent. When it reacts in the equation AQA gave, it can't be a reducing agent, because it won't lose any more electrons.

Cd is not an oxidising agent, it won't gain more electrons. But it is a strong reducing agent (strongest in the table) because it is the best at giving away it's electrons

[Msd27]

(Original post by vedderfan94)
It's talking about the weakest oxidising agent. Why are so many people overlooking this key word?

how have i overlooked this?

[vedderfan94]

(Original post by Newbie123)
Cd is not an oxidising agent, therefore it's incorrect to say it's the weakest oxidising agent.

The question before that question asked you for the definition of an oxidising agent - which is, an electron acceptor.

Cd doesn't accept electrons.

Which is why it is the weakest oxidising agent. Look at it this way: the most negative value of E is the strongest reducing agent (something that is oxidised). Cd has the most negative E value and therefore is oxidised, because it cannot be reduced.

[Newbie123]

(Original post by ayseta)
You're saying that Cd lacks something that oxidising agents have. The question is asking for the WEAKEST oxidising agent...

You've misinterpreted my use of the word "lack", so let me make it clearer.

Cd cannot possibly be an oxidising agent, at all, whatsoever, in any shape or form.

What's an oxidising agent? An electron acceptor.

I'll repeat, if I ask you for the weakest swimming fish, would you say "a dog"? No, because a dog isn't a fish. Comparably, Cd doesn't accept electrons - so it's never an oxidising agent.

[tony_dolby]

(Original post by Newbie123)
Cd is not an oxidising agent, therefore it's incorrect to say it's the weakest oxidising agent.

The question before that question asked you for the definition of an oxidising agent - which is, an electron acceptor.

Cd doesn't accept electrons.

Bang on.

Oxidizing agent is the key phrase here. I haven't had time to go through this paper because I didn't have any students sitting it this year, but it looks quite challenging.

[James24993]

Aren't the phrases weakest oxidising agent and strongest reducing agent interchangeable?

[stephie.u3]

www.facebook.com/Thechem5paperwasadisgrace

[vedderfan94]

(Original post by Newbie123)
You've misinterpreted my use of the word "lack", so let me make it clearer.

Cd cannot possibly be an oxidising agent, at all, whatsoever, in any shape or form.

What's an oxidising agent? An electron acceptor.

I'll repeat, if I ask you for the weakest swimming fish, would you say "a dog"? No, because a dog isn't a fish. Comparably, Cd doesn't accept electrons - so it's never an oxidising agent.

You are completely ignoring the keyword - weakest.

[wibletg]

(Original post by vedderfan94)
It's talking about the weakest oxidising agent. Why are so many people overlooking this key word?

They aren't.

The weakest oxidising agent is itself reduced.

The one that was the weakest in the table at being reduced was the Cd(OH)2 compound.

If it had talked about strongest reducing agent then you could have put Cd.