Gen chem question

[299678]

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PbO(s) + Co(g) -> Pb (s) + CO2 (g)
which one is oxidizing agent

I am so confusing between PbO and Pb. The correct answer is PbO, but why not for Pb? OS number for Pb is reduced from +2 to 0, so can be oxidizing agent. Please explain me in detail to support your answer. Thank you

 

[dentalWorks]

lets see if I remember this correctly...

Oxidation = loosing electrons
Reduction = gaining of electrons

Oxidizing agent = its an agent that makes things around it become oxidized, meaning they loose thier electrons to it, so... oxidizing agent = the one that gets reduced (gains electrons)

Pay attention to Co(g), it became Co2, meaning the Co(g) became oxidized.

Since Co(g) got oxidized, then the PbO(s) got reduced...

so PbO(s) = oxidizing agent (It made the Co(g) become oxidized)

 

[dentalWorks]

A easy way to remember this (BUT DON'T ALWAYS RELAY ON THIS CAUSE IT ONLY WORKS WHEN YOU HAVE OXYGEN IN THE FORMULAS)

Oxidation = gaining of oxygen atoms, or loosing Hydrogen atoms
Reduction = loosing oxygen atoms, or gaining Hydrogen atoms

These are 100% true but DON'T always relay on them cause sometime you don't have hydrogens or oxygens.

 

[Avery07]

lets see if I remember this correctly...

Oxidation = loosing electrons
Reduction = gaining of electrons

Oxidizing agent = its an agent that makes things around it become oxidized, meaning they loose thier electrons to it, so... oxidizing agent = the one that gets reduced (gains electrons)

Pay attention to Co(g), it became Co2, meaning the Co(g) became oxidized.

Since Co(g) got oxidized, then the PbO(s) got reduced...

so PbO(s) = oxidizing agent (It made the Co(g) become oxidized)

Are you 100% sure on this? I would have said that Co is reduced by gaining the O atom and is therefore the oxidizing agent.

I've always thought if you gain atoms you are reduced -- no matter if its hydrogen or oxygen. Good to get this cleared up.

 

[UndergradGuy7]

Are you 100% sure on this? I would have said that Co is reduced by gaining the O atom and is therefore the oxidizing agent.

I've always thought if you gain atoms you are reduced -- no matter if its hydrogen or oxygen. Good to get this cleared up.

I think the original post has an error. "Co" is supposed to be "CO" carbon monoxide and not the element Cobalt. Otherwise where is the element Co in the products? So The C in CO went from +2 to +4 in CO2. It became oxidized. So the thing that oxidized it is PbO. I agree with dentalworks.

 

[299678]

Thank you for your detailed explanation. +1 But my question is Pb can be still oxidizing agent since it gain 2 electrons

 

[dentalWorks]

Are you 100% sure on this? I would have said that Co is reduced by gaining the O atom and is therefore the oxidizing agent.

I've always thought if you gain atoms you are reduced -- no matter if its hydrogen or oxygen. Good to get this cleared up.

Im not 100% sure (haven't studied Gen Chem since my DAT) but Im 95% sure on this.

Thank you for your detailed explanation. +1 But my question is Pb can be still oxidizing agent since it gain 2 electrons

Okay, first of all, when you get questions about which is oxidizing / reducing agent, DON'T LOOK AT BOTH THE LEFT SIDE OF ARROW AND RIGHT SIDE OF ARROW IN THE SAME TIME. Pick one side and stick with it.

PbO(s) + Co(g) -> Pb (s) + CO2 (g)
So if your looking at the blue side, one of them gets oxidized, and the other gets reduced (thats the 101-rule of redox equations). PbO(s) "gets" reduced (its the oxidizing agent) while Co(g) "gets" oxidized (its the reducing agent)

by the same rule, if you were looking only at the black (right) side, you can see that CO2(g) "gets" reduced (its the oxidizing agent) while the Pb(s) "gets" oxidized (its the reducing agent)

 

[Avery07]

I think the original post has an error. "Co" is supposed to be "CO" carbon monoxide and not the element Cobalt. Otherwise where is the element Co in the products? So The C in CO went from +2 to +4 in CO2. It became oxidized. So the thing that oxidized it is PbO. I agree with dentalworks.

I meant CO and not Co but still don't understand why CO --> CO2 isn't reduction.

 

[dentalWorks]

I meant CO and not Co but still don't understand why CO --> CO2 isn't reduction.

Red = oxidation number values

C(+2)O(-2) --> C(+4)O(-2)2

Look at what happen to the Carben, it went from +2 --> +4.... It lost 2 electrons (oxidation) and became even more possitive

 

[Avery07]

Red = oxidation number values

C(+2)O(-2) --> C(+4)O(-2)2

Look at what happen to the Carben, it went from +2 --> +4.... It lost 2 electrons (oxidation) and became even more possitive

Well when you put it like that, it's hard to argue. 👍

 

[UCB05]

I've always thought if you gain atoms you are reduced -- no matter if its hydrogen or oxygen. Good to get this cleared up.

That's definitely not the case. NAD+ gets reduced with the addition of H- to NADH. In this case, CO gets oxidized with the addition of O to CO2.

When asked for an agent of either sort, look at the reactant side, and look at the whole molecule, in this case PbO. Notice it says PbO(s). It doesn't exist as an ion in solution, so you can't say Pb+2 is the oxidizing agent. Look at what exists in the reaction conditions given.

 

[Ibracadabra]

Oxidation= either gain of Oxygen, or Losing Hydrogen or electrons
Reduction=gaining of Hydrogen or electrons, or Losing Oxygen

I think all the sdners explained the question itself well.. so I'll skip it 😀