Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: xstrae on June 15, 2006, 11:58:25 AM
-
How many moles of KMnO4 will be needed to react with one mole of sulphite ion in acidic solution?
Can someone please guide me with the equation?
Thanks!
-
balanced equation
-
u mean like this?
2 KMnO4 + 3H2SO3 ----> K2SO3 + 2MnSO3 + 3H2O + 5(O)
This indicates that number of moles of KMnO4 required is 2/3. However the book i got this question from says that the right answer is 2/5. Can u please explain if what i did is right?
-
Sulfite was meant to react, but in your equation it is spectator.
-
allright i have no clue. can u tell me how it should react? and how many moles of KMnO4 are needed?
-
Main products are Mn2+ and SO42-.
-
i am sorry i still dont understand. can u please explain this? i am not very good at chemistry.
-
Balance your reactions assuming MnO4- + SO32- reactants and Mn2+ + SO42- products.
Check this out: balancing redox reactions with half-reaction method (http://www.chembuddy.com/?left=balancing-stoichiometry&right=half-reactions-method).
-
thanks a lot! i finally understood it. u rock!
-
hey i read all the solubility rules and i think i got it. But this new problem stumps me.
How many moles of KMnO4 will be be needed to react completely with one mole of ferrous oxalate in acidic solution???
First of all, is ferrous oxalate soluble?if so what are the products? can u help me out once more?
-
Is this equation right? ???
MnO4- +Fe2+ C2O4 2- -------> Mn2+ + CO2 + Fe3+
it isnt balanced. but are the reactants and products correct?
-
Is this equation right? ???
MnO4- + C2O4 -------> Mn2+ + CO2 + Fe3+
No, it isn't. It's not balanced and incomplete.
For example, why didn't you write iron among the reagents?
-
ya i am sorry. i left it out accidenly. anyway, i am quite sure its still wrong. sorry, I am just a beginner in chemistry :-[. can u help me out? :-\
-
I can't, NOW ;).
In the meantime, if you know them, try writing the 3 half reactions: http://www.science.uwaterloo.ca/~cchieh/cact/c123/halfreac.html
reduction of KMnO4 (in acid)
oxidation of Fe2+
oxidation of C2O42-
Then, I'll be pleased to help you. :)
-
ok i think i finally worked out the equation. I think its wrong though. anyway here goes:
2MnO4- + 16H+ + 5C2O42 ----> 10CO2 + 2Mn2+ + 8H2O
do i just add a fe2+ to the reactants and fe3+ to the product side and balnce it? the question is really stupid isnt it? :( i suck at chemistry.
-
Go on: add the iron and balance the chemical equation.
At the moment, the charges aren't balanced yet.
-
2MnO4- + 16H+ + 5C2O42- +Fe2+ ----> 10CO2 + 2Mn2+ + 8H2O + Fe3+ + e-
is this right?
-
Go on: add the iron and balance the chemical equation.
Albert - try it by yourself first. That's pretty bad advice.
At the moment, the charges aren't balanced yet.
Yes they are - note konichiwa2x did a mistake in oxalate formula (last digit is a charge).
Edit: I am referring to the earlier reaction, not the one with Fe.
-
No, it's not.
First of all, I am sure you're aware of the fact that the charges aren't balanced: 16 positive ones among the reagents vs. 6 among the products. They have to be the same.
Then, you must not have electrons. NEVER! ;)
Don't you want to use half reactions? It's extremely easier.
-
2MnO4- + 16H+ + 5C2O4 +Fe2+ ----> 10CO2 + 2Mn2+ + 8H2O + Fe3+ + e-
is this right?
No, it is not - for million of reasons. But first of all: it doesn't make sense to try to balance such reaction.
Note, that you have three redox systems here - oxidizer (permanganate) and two reducing agents (oxalate and Fe2+). You may separatley balance oxidation of oxalate to carbon dioxide, or of Fe2+ to Fe3+. Then you can add these ractions in any way you want, multiplying them by any integer nubers you want - and what you will get will be new balanced equation. Does it make sense? No.
Please read my lecture on reaction balacing failures (http://www.chembuddy.com/?left=balancing-stoichiometry&right=balancing-failure).
-
Go on: add the iron and balance the chemical equation.
Albert - try it by yourself first. That's pretty bad advice.
I know it Borek. :D
I am trying to persuade konichiwa2x to use half reactions method. :)
-
Albert - try it by yourself first. That's pretty bad advice.
I know it Borek. :D
I am trying to persuade konichiwa2x to use half reactions method. :)
Half reaction method will not help, idea of balancing system containing more than 2 redox system is faulty.
-
allright is the write way to do it by writing down the indivual reactions and adding them?
-
allright is the write way to do it by writing down the indivual reactions and adding them?
No, as you will have as many reactions looking as properly balanced as you want. Read text at the link provided - there are examples of such reactions.
Or take a look here:
http://www.chemicalforums.com/index.php?topic=8057.msg38533#msg38533
-
OK, due to popular request (sent in private emails by those ashamed that they don't follow ;) ) here comes detailed explanation prepared (partially) using my EBAS program.
First of all, we have two balanced reactions. Oxidation of oxalate:
2MnO4- + 16H+ + 5C2O42- -> 10CO2 + 2Mn2+ + 8H2O
and oxidation of Fe2+
MnO4- + 5Fe2+ + 8H+ -> Mn2+ + 5Fe3+ + 4H2O
We can add these two reactions to get:
3MnO4- + 24H+ + 5C2O42- + 5Fe2+ -> 10CO2 + 3Mn2+ + 12H2O + 5Fe3+
and we get balanced equation - but we can for example add first equation multiplied by 7 to second reaction multiplied by 11 (we will be forced to find out smallest coefficients then) to get:
5MnO4- + 40H+ + 7C2O42- + 11Fe2+ -> 14CO2 + 5Mn2+ + 20H2O + 11Fe3+
Which one is correct? Note that I can multiply these reaction before adding them by different numbers and I will get as many correctly balanced reactions as I want, making the question even harder, as you will have to select 'correct' equation out of infinite set..
Thing is, none of them describes real situation. Real situation is - there are two, separate reaction taking place simultaneously. We can write speratae, balanced reactions for both of them, but adding them just doesn't make sense.
-
ok thanks for explaining that. by the way what is an EBAS?
-
ok thanks for explaining that. by the way what is an EBAS?
Check my signature.