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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: April09 on June 23, 2010, 01:39:02 AM

Title: products formed from Fe(NH4)2(SO4)2·6H2O + KMnO4 ?
Post by: April09 on June 23, 2010, 01:39:02 AM

Hello there :)

I was trying to find the products that would be formed from the reaction of:

Fe(NH4)2(SO4)2·6H2O  +   KMnO4  -->  ??

From a lab session I've found that oxygen gas is one of the products and that Fe(NH4)2(SO4)2·6H2O gets oxidised, but I'm not very sure about what other products are formed. I've tried looking for the answers on google but all I've found are the redox equations. I've included them in case they're helpful:

MnO4- + 8 H+ + 5e-  -->  Mn+2 + 4 H2O                       OXIDATION

Fe +2 --> Fe +3 + e-                                                  REDUCTION

MnO4-+ 5 Fe+2 + 8 H+ --> Mn+2 + 5 Fe+3 + 4 H2O          REDOX EQN

Could someone help me with this or point me in the right direction/introduce good resources for reference? Thank you in advance! :)

Title: Re: products formed from Fe(NH4)2(SO4)2·6H2O + KMnO4 ?
Post by: AWK on June 23, 2010, 02:10:44 AM

Quote

MnO4-+ 5 Fe+2 + 8 H+ --> Mn+2 + 5 Fe+3 + 4 H2O

Yes, this is a simple oxidation of Fe(II) to Fe(III). Balancing for ionic reaction is correct

Title: Re: products formed from Fe(NH4)2(SO4)2·6H2O + KMnO4 ?
Post by: April09 on June 23, 2010, 04:49:46 AM

Hey there AWK, thank you for replying! :D Well actually what i was asking was: what are the products that are formed? I'm trying to write the full chemical equation instead of just the ionic reaction  ???  Thank you  :)

Title: Re: products formed from Fe(NH4)2(SO4)2·6H2O + KMnO4 ?
Post by: Borek on June 23, 2010, 05:24:43 AM

In general there is no such thing as a 'full equation'. You end up with solution containing mixture of ions, not well defined salts.

In this particular case you may list all possible (and necessary) sulfates as products, but when there are several anions things get messy.

Title: Re: products formed from Fe(NH4)2(SO4)2·6H2O + KMnO4 ?
Post by: April09 on June 23, 2010, 07:01:39 AM

thank you for your reply, Borek! :) does this mean that the products of this reaction are: Mn+2 ions, Fe+3 ions, and water? that's all?  :P

Title: Re: products formed from Fe(NH4)2(SO4)2·6H2O + KMnO4 ?
Post by: AWK on June 24, 2010, 01:58:26 AM

Fe(NH4)2(SO4) is a 1:1 (molar) mixture of FeSO4  and (NH4)2SO4.
Only iron(II) sulfate is oxidized by permanganate

Title: Re: products formed from Fe(NH4)2(SO4)2·6H2O + KMnO4 ?
Post by: April09 on June 25, 2010, 12:19:42 AM

Thank you for replying, AWK :) I think I understand now :D As a side question, the solution turns brown after I add KMnO4. Is this because of FeSO4 being oxidised? Thank you so much :)

Title: Re: products formed from Fe(NH4)2(SO4)2·6H2O + KMnO4 ?
Post by: Woofuls on June 25, 2010, 01:01:21 AM

manganese dioxide is totally brown ;)

Title: Re: products formed from Fe(NH4)2(SO4)2·6H2O + KMnO4 ?
Post by: AWK on June 25, 2010, 01:59:25 AM

Quote from: April09 on June 25, 2010, 12:19:42 AM

Thank you for replying, AWK :) I think I understand now :D As a side question, the solution turns brown after I add KMnO4. Is this because of FeSO4 being oxidised? Thank you so much :)

You should add same H2SO4 before addition of permanganate, otherwise MnO₂ is formed