Question

For the cell prepared from electrode $A$ and $B$, electrode $A$: $\frac{C{r}_2{O}_7{}^{2-}}{C{r}^{3+}}$ , $E^o{}_{red}$ = + 1.33 V and electrode $\frac{F{e}^{3+}}{F{e}^{2+}}$, $E^o{}_{red}$ = 0.77 V, which of the following statement is not correct?

• A. The electrons will flow $B$ to $A$ (in the outer circuit) when connections are made
• B. The standard e.m.f. of the cell will 0.56 V
• C. $A$ will be positive electrode
• D. None of the above

Answer 1

Answer: (C)

$A$ will be positive electrode

$E_{red}^o$ of $C{r}_2{O}_7^{2-}⟶C{r}^{+3}$ is higher, thus it will take place at cathode.

At cathode, electrons are present, when ions from the solution move towards cathode, they accept the electron and get reduced at cathode.

Thus, cathode is a negatively charged electrode.

Here electrode $A$ is cathode. Thus, $A$ must be negatively charged.

Hence, statement $C$ is incorrect.