How to separate this redox reaction into two half reactions?

Chemistry and homework help forum.

Organic Chemistry, Analytical Chemistry, Biochemistry, Physical Chemistry, Computational Chemistry, Theoretical Chemistry, High School Chemistry, Colledge Chemistry and University Chemistry Forum.

Share your chemistry ideas, discuss chemical problems, ask for help with scientific chemistry questions, inspire others by your chemistry vision!

Please feel free to start a scientific chemistry discussion here!

Discuss chemistry homework problems with experts!

Ask for help with chemical questions and help others with your chemistry knowledge!

Moderators: expert, ChenBeier, Xen

Post Reply
User avatar
Dhamnekar Winod
Sr. Member
Sr. Member
Posts: 35
Joined: Sat Nov 21, 2020 10:14 am
Location: Mumbai[Bombay],Maharashtra State,India

How to separate this redox reaction into two half reactions?

Post by Dhamnekar Winod »

How to separate this redox reaction into two half reactions?

\( HCHO(l) + 2[Ag(NH_3)_2]^+(aq) + 3OH^-(aq) \rightarrow 2Ag(s) + HCOO^-(aq) + 4NH_3(aq) + 2H_2O(l)\)
Any science consists of the following process. 1) See 2)Hear 3)Smell,if needed 4)Taste, if needed 5)Think 6)Understand 7)Inference 8)Take decision [Believe or disbelieve, useful or useless, true or false, cause or effect, any other criteria]
User avatar
ChenBeier
Distinguished Member
Distinguished Member
Posts: 537
Joined: Wed Sep 27, 2017 7:25 am
Location: Berlin, Germany

Re: How to separate this redox reaction into two half reactions?

Post by ChenBeier »

HCHO + 3 OH- => HCOO- + 2 H2O + 2 e- Oxidation

[Ag(NH3)2]+ + e- => Ag + 2 NH3 Reduction
User avatar
Dhamnekar Winod
Sr. Member
Sr. Member
Posts: 35
Joined: Sat Nov 21, 2020 10:14 am
Location: Mumbai[Bombay],Maharashtra State,India

Re: How to separate this redox reaction into two half reactions?

Post by Dhamnekar Winod »

You have given oxidation and reduction reactions in your reply. But in other chemistry notes, these reactions are given as below:

\(H_2O(l) + HCHO(l) \rightarrow HCOO^-(aq) +3H^+ +2e^-\Rightarrow\) OXIDATION


\( [Ag(NH_3)_2]^+ (aq) +e^- \rightarrow Ag(s) + 2NH_3(aq) + 2H_2O(l) \Rightarrow\) REDUCTION

What is your explanation for these half reactions?
Any science consists of the following process. 1) See 2)Hear 3)Smell,if needed 4)Taste, if needed 5)Think 6)Understand 7)Inference 8)Take decision [Believe or disbelieve, useful or useless, true or false, cause or effect, any other criteria]
User avatar
ChenBeier
Distinguished Member
Distinguished Member
Posts: 537
Joined: Wed Sep 27, 2017 7:25 am
Location: Berlin, Germany

Re: How to separate this redox reaction into two half reactions?

Post by ChenBeier »

It depends which pH you have. If its acidic environment then H+ is used, in alcaline condition OH-.

But the right one is the alcaline one in this case. The Diamminsilver is not stable in acidic condition.
User avatar
Dhamnekar Winod
Sr. Member
Sr. Member
Posts: 35
Joined: Sat Nov 21, 2020 10:14 am
Location: Mumbai[Bombay],Maharashtra State,India

Re: How to separate this redox reaction into two half reactions?

Post by Dhamnekar Winod »

We get the following redox reactions by adding the two half reactions \(H_2O (l) + HCHO(l) \rightarrow HCOO^-(aq) + 3H^+ + 2e^- \tag{Oxidation} \) and \([Ag(NH_3)_2]^+(aq) + e^- \rightarrow Ag(s) + 2NH_3(aq) + 2H_2O(l) \times 2 \tag{Reduction}\)

\(= HCHO(l) + 2[Ag(NH_3)_2]^+(aq) \rightarrow HCOO^-(aq) +3H^+ + 2Ag(s) +4NH_3(aq) + 3H_2O(l)\)

which is different from the original redox equation namely \( HCHO(l) + 2[Ag(NH_3)_2]^+ (aq) + 3OH^- (aq) \rightarrow 2Ag(s) + HCOO^-(aq) +4NH_3(aq) + 2H_2O(l) \)

Where is the mistake? where are we wrong? Why did such discrepancy occur?

Would any chemistry expert answer these questions?
Any science consists of the following process. 1) See 2)Hear 3)Smell,if needed 4)Taste, if needed 5)Think 6)Understand 7)Inference 8)Take decision [Believe or disbelieve, useful or useless, true or false, cause or effect, any other criteria]
User avatar
ChenBeier
Distinguished Member
Distinguished Member
Posts: 537
Joined: Wed Sep 27, 2017 7:25 am
Location: Berlin, Germany

Re: How to separate this redox reaction into two half reactions?

Post by ChenBeier »

Did you read my answer above. You are wrong because [Ag(NH3)2] + is not existing in acidic conditions.

Mathematically you can write both equations, but only one will happen in practise.
Post Reply