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Qualification => Subject Doubts => GCE AS & A2 Level => Sciences => Topic started by: Saladin on February 15, 2010, 08:34:14 pm

Title: Chemistry Question: Overall reaction
Post by: Saladin on February 15, 2010, 08:34:14 pm
Help me to find the overall reaction of these two equations:

Cr22-O7+14H++6e------>2Cr3++7H2O

and

CH3CH2OH---->CH3COOH+4H++4e-
Title: Re: Chemistry Question: Overall reaction
Post by: nid404 on February 16, 2010, 05:34:50 am
I assume it's
Cr2O7 2- + 14H++6e----->2Cr3++7H2O

&

CH3CH2OH + H2O
---->CH3COOH+4H++4e-

First step you make the no of electrons equal

6 and 4...1st common multiple is 12....multiply the 1st eqn by 2 and second by 3
Cr2O7 2- + 14H++6e----->2Cr3++7H2O X2
2Cr2O7 2- + 28H++12e----->4Cr3++14H2O

CH3CH2OH+H2O---->CH3COOH+4H++4e-  X3
3CH3CH2OH+3H2O---->3CH3COOH+12H++12e-

Now add the 2 eqn
U get
2Cr2O7 2- + 28H++12e-+3CH3CH2OH+3H2O------------>4Cr3++14H2O+3CH3COOH+12H++12e-

2Cr2O7 2- + 28H++12e-+3CH3CH2OH+3H2O------------>4Cr3++14H2O+3CH3COOH+12H++12e-
Cancel the like terms

2Cr2O7 2-+(28-12)H++3CH3CH2OH----->4Cr3++(14-3)H2O+3CH3COOH

So finally
2Cr2O7 2-+16H++3CH3CH2OH----->4Cr3++11H2O+3CH3COOH

Title: Re: Chemistry Question: Overall reaction
Post by: Saladin on February 16, 2010, 07:08:18 am
I just found out the answer to this 6 minutes after I posted and then went to sleep.

Thanx anyway, for taking the time to answer the question. Its just when something takes me more than a minute to solve, I get frustrated.
Title: Re: Chemistry Question: Overall reaction
Post by: nid404 on February 16, 2010, 07:16:23 am
Quote from: The Dude 321 on February 16, 2010, 07:08:18 am
I just found out the answer to this 6 minutes after I posted and then went to sleep.

Thanx anyway, for taking the time to answer the question. Its just when something takes me more than a minute to solve, I get frustrated.

No problem :)
Title: Re: Chemistry Question: Overall reaction
Post by: Saladin on February 16, 2010, 07:34:48 am
How long did it take to type that, it is a very nicely written answer.
Title: Re: Chemistry Question: Overall reaction
Post by: nid404 on February 16, 2010, 07:49:53 am
Quote from: The Dude 321 on February 16, 2010, 07:34:48 am
How long did it take to type that, it is a very nicely written answer.

About 6-7  min

Thanks :)
Title: Re: Chemistry Question: Overall reaction
Post by: Saladin on February 16, 2010, 07:54:45 am
And I thought I was fast.

hehe. It would take me around 7 aswell.

I am deeply sorry that u had to waste that much time.
Title: Re: Chemistry Question: Overall reaction
Post by: nid404 on February 16, 2010, 08:03:41 am
No problem at all...I kinda got some practice too...so it's k