Chemistry redox reactions?

[qwerty1]

Can someone help me with redox reactions . It is urgent.

 

Are these half-reactions correct :

It is from this equation

Mn2+ + NaBiO3 + H+ -----> MnO2 + Bi3+ + Na+ + H2O

 

 

Mn2+ ---> MnO2 + 2e-

NaBiO3 + 2e- ---> Bi3+

 

 

This is another equation :

 

Mn2+ + NaBiO3 + H+ -----> MnO4- + Bi3+ + H2O + Na+

 

I need the oxidation reduction equation for it . Please explain it to me as you do it. Don't just

answer it

 

This is another equation:

 

MnO4- + H2O2 + H+ ------> Mn2+ + O2

 

I don't understand which oxygen will be oxidized since there are two of them on the left

one is in MnO4 and one in H2O2...please give me an explanation

 

Thanks. I appreciate the help

 

Report to moderator 98.25.95.12

[Pwyll Pendefig Dyfed]

Can someone help me with redox reactions . It is urgent.

 

Are these half-reactions correct :

It is from this equation

Mn2+ + NaBiO3 + H+ -----> MnO2 + Bi3+ + Na+ + H2O

 

 

Mn2+ ---> MnO2 + 2e-

NaBiO3 + 2e- ---> Bi3+

 

In terms of the electrons, it looks correct.

 

This is another equation :

 

Mn2+ + NaBiO3 + H+ -----> MnO4- + Bi3+ + H2O + Na+

 

I need the oxidation reduction equation for it . Please explain it to me as you do it. Don't just

answer it

Mn2+ --> MnO4- is going from +2 (due to it's charge) to +7, so it's being oxidised.

NaBiO3 --> Bi3+ (like in the previous question) is going from +5 to +3, so it's being reduced.

The Na and H remains at +1, the O remains at -2

 

This is another equation:

 

MnO4- + H2O2 + H+ ------> Mn2+ + O2

 

I don't understand which oxygen will be oxidized since there are two of them on the left

one is in MnO4 and one in H2O2...please give me an explanation

 

Thanks. I appreciate the help

 

The oxygens in the MnO4 and in H2O2 will be oxidised, as they're forming O2. All the oxygens are losing electrons, so they're all being oxidised.

Edited February 22, 2011 by ceribethlem

[hypervalent_iodine]

Ceribethlam,

 

For future reference, try not to simply give out answers to what are clearly homework questions. Secondly, one of your answers was wrong. So if you are going to give help to people in chemistry in the future, please check you are giving correct advise.

 

Qwerty,

 

A few things you need to take notice of when doing these questions:

 

The total ionic charge of a species is equal to the sum of the charges of its components. There are a few rules to pay attention to when working out the charge on each individual atom within a molecule. The major ones for you are that oxygen and hydrogen, when present as part of a compound, have charges of 2- and 1+ respectively. The exception for oxygen is in the case of peroxides (such as H2O2), where it has a charge of 1-. The other thing to remember is that molecular species, such as O2, N2 etc have a charge of 0. You can use this information quite to work out the charges of other species within a compound, or conversely, the net charge of the compound itself. As an example, if knowing that H and O have 1+ and 2- charge respectively, I can say that the net charge of a water molecule is 0. This is because the net charge of the compound is equal to the sum if the charges of it's components. Thus, the net charge of water = 2 [+1] (for the 2 hydrogens) + [-2] = 0. You could also work the reverse way to get the charge of say, oxygen, where you know the net charge of the compound it's in (water in this example, so 0). The correlations that ceribethlam made regarding which species were being oxidized and reduced were correct, but you need to watch for that peroxide in the last question. The oxygens in the permanganate are all 2-, but the peroxide oxygens are not.

 

Hope the helps.

Edited February 24, 2011 by hypervalent_iodine

[Pwyll Pendefig Dyfed]

Ceribethlam,

 

For future reference, try not to simply give out answers to what are clearly homework questions.

 

 

Sorry. Is it possible to edit the reply?

Edited February 28, 2011 by ceribethlem

[swansont]

Sorry. Is it possible to edit the reply?

 

There's probably no point to doing so now. The genie is out of the bottle.