In a dry cell, NH3 Liberated by the reaction does not built up gas pressure. Explain.

Dear Student,

Reactions Involved in a Dry Cell:

At Cathode:   2NH4(aq)+ + 2 e- Reduction 2NH3(g) + H2(g)
At Anode:     Zn(s) Oxidation Zn(aq)2+ + 2 e-
Now, These two gases thus formed would have burst the cell, but this does not happen due to the other 2 reactions that are going on in the cell which are as follows:
  • Zn(aq)2+ + 2NH3(g) + 2Cl(aq)-  ZnNH32Cl2(s)
  • 2MnO2(s) + H2(g)  Mn2O3(s) + H2O(l)

So, in the first reaction, Ammonia gas (NH3) combines with Zn2+ ions.
And, in the second reaction, Hydrogen gas (H2) is Oxidised by MnO2 .

Hence, No gas pressure builds up in the Dry cell.

Hope this information clears your doubts about the topic.

Looking forward to hear from you again!!

Regards

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