A concentration cell constructed from two hydrogen electrodes, both with P H2 =

Question

A concentration cell constructed from two hydrogen electrodes, both with PH2 = 1.00. One electrode is immersed in pure H2O and the other in 6.0 M hydrochloric acid. What is the emf generated by the cell and what is the identity of the electrode that is immersed in hydrochloric acid? (a) - 0.23 V, cathode, (b) 0.46 V, anode, (c) 0.023 V, anode, (d) 0.23 V, cathode, (e) 0.23 V, anode.

- I have seen this question answered before on Chegg, the one thing that I don't understand is how the conclusion the overall cell reaction is this: H+ (aq, 6.0 M) -> H+ (aq, 1 x 10-7 M) - What I do not understand is where the 1 x 10-7 Molarity concentration came from.

Explanation / Answer

Concentration of H+ in pure H2O = 1 x 10-7M

We have Nernst equation,

Ecell = E0 -RT/nF ln(Q) = E0 –[RT/nF]xln[H+(1 x 10-7M)]/[H+(6M)]

Here, E° = 0 and n=1

Therefore, Ecell = 0 -[(8.314)×(298)]/(96485)]ln[(1.0 x 10-7)/(6)] = -(-0.46 V) = 0.46V

At cathode, reduction occurs. Therefore, electrode immersed in HCl is cathode

Answer : 0.46 V and cathode

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