Question

# Electra - "Hmm, this looks tricky" At 25∘C, Cr3++e−→Cr2+, given E0=−0.424 VCr2++2e−→Cr(s), given E0=−0.9 VFind E0 at 25∘C for Cr3+(aq)+3e−→Cr(s) Electra was completely stumped. Seems like you need a way to add electrode potentials. Please tell her the answer.

A
0.741 V
No worries! We‘ve got your back. Try BYJU‘S free classes today!
B
- 0.741 V
Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses
C
-1.324 V
No worries! We‘ve got your back. Try BYJU‘S free classes today!
D

-0.476 V

No worries! We‘ve got your back. Try BYJU‘S free classes today!
Open in App
Solution

## The correct option is C - 0.741 VWe cannot add the electrode potentials directly because they are an intensive property. Think about density and temperature for example. You cannot just add the density of a rock and a paper directly to get the final density. Gibb’s energy on the other hand, is an extensive property. We can add it directly. Adding the first two reactions, we get the third equation and using the free energy concept, we have ΔG01+ΔG02=ΔG03; −n1E01F−n2E02F=−n3E03F (n = number of electrons involved) E03=n1E01+n2E02n3=1×(−0.424)+2×(−0.900)3=−0.741V

Suggest Corrections
0
Related Videos
Gibb's Energy and Nernst Equation
CHEMISTRY
Watch in App