Question

For the cell $Zn\left(s\right)|Z{n}^{2+}||C{u}^{2+}|Cu\left(s\right)$, the standard cell voltage, $E_{cell}^{\ominus }$ is 1.10 V. When a cell using these reagents was prepared in the lab, the measured cell voltage was $0.98V$. One possible explanation for the observed voltage is :

• A. There were 2.00 mol of $Z{n}^{2+}$ but only 1.00 mol of $C{u}^{2+}$.
• B. The Zn electrode had twice the surface of the Cu electrode.
• C. The $\left[Z{n}^{2+}\right]$ was larger than the $\left[C{u}^{2+}\right]$.
• D. The volume of the $\left[Z{n}^{2+}\right]$ solution was larger than the volume of the $C{u}^{2+}$ solution.

Answer 1

Answer: (C)

The $\left[Z{n}^{2+}\right]$ was larger than the $\left[C{u}^{2+}\right]$.

As we know,

$E_{cell}=E_{cell}^{\ominus }-\frac{0.0591}{2}log,\frac{\left[Z{n}^{2+}\right]}{\left[C{u}^{2+}\right]}$

$E_{cell}<E_{cell}^{\ominus }\Rightarrow \left[Z{n}^{2+}\right]>\left[C{u}^{2+}\right]$