Is it correct the next equation: C7H14+H2SO4+K2Cr2O7=C3H6O+C4H8O+K2SO4+Cr2(SO4)3+H2O?
Then how I can balance it?
Redox equation - help!
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Re: Redox equation - help!
Assuming C7H14 is 3-heptene, CH3CH2CH=CHCH2CH2CH3, then yes, it will produce 1-propanal and 1-butanal... to start with at least. In excess, chromic acid will continue to oxidize the alkanals further into carboxilic acids.Expelliarmus9 wrote:Is it correct the next equation: C7H14+H2SO4+K2Cr2O7=C3H6O+C4H8O+K2SO4+Cr2(SO4)3+H2O?
Then how I can balance it?
Firstly, let's just consider the active ingredients (remove the passive observers). With R as CH3CH2 and R' as CH3CH2CH2.
RCH=CHR' + Cr2O7-2 + H+ => RCH=O + R'CH=O + Cr+3 + H2O
Balance the chromium:
RCH=CHR' + Cr2O7-2 + H+ => RCH=O + R'CH=O + 2 Cr+3 + H2O
Balance the charges:
RCH=CHR' + Cr2O7-2 + 8 H+ => RCH=O + R'CH=O + 2 Cr+3 + H2O
Balance the hydrogen:
RCH=CHR' + Cr2O7-2 + 8 H+ => RCH=O + R'CH=O + 2 Cr+3 + 4 H2O
Balance the oxygen, and incidentally the organics:
1.5 RCH=CHR' + Cr2O7-2 + 8 H+ => 1.5 RCH=O + 1.5 R'CH=O + 2 Cr+3 + 4 H2O
Adjust to the Lowest Integer Solution:
3 RCH=CHR' + 2 Cr2O7-2 + 16 H+ => 3 RCH=O + 3 R'CH=O + 4 Cr+3 + 8 H2O
Add back the observer ions (as 4 potassium cations and 8 sulphate anions) to neutralise charges:
3 RCH=CHR' + 2 K2Cr2O7 + 8 H2SO4 => 3 RCH=O + 3 R'CH=O + 2 K2SO4 + 2 Cr2(SO4)3 + 8 H2O
Thus:
3 CH3CH2CH=CHCH2CH2CH3 + 2 K2Cr2O7 + 8 H2SO4 => 3 CH3CH2CH=O + 3 CH3CH2CH2CH=O + 2 K2SO4 + 2 Cr2(SO4)3 + 8 H2O
Or if you will:
3 C7H14 + 2 K2Cr2O7 + 8 H2SO4 => 3 C3H6O + 3 C4H8O + 2 K2SO4 + 2 Cr2(SO4)3 + 8 H2O
Last edited by GrahamKemp on Mon Jul 23, 2012 8:20 pm, edited 1 time in total.