Question

In a Daniell cell constructed in the laboratory, the voltage observed was $0.9V$ instead of $1.1V$ of the standard cell. A possible explanation is

• A. $\left[Z{n}^{2+}\right]>\left[C{u}^{2+}\right]$
• B. $\left[Z{n}^{2+}\right]<\left[C{u}^{2+}\right]$
• C. $Zn$ electrode has twice the surface of $Cu$ electrode
• D. Mole ratio of $Z{n}^{2+}:C{u}^{2+}$ is $2:1$

Answer 1

Answer: (A)

$\left[Z{n}^{2+}\right]>\left[C{u}^{2+}\right]$

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

$E_{cell}=1.1-\frac{0.0591}{2}\log \frac{\left[Z{n}^{2+}\right]}{\left[C{u}^{2+}\right]}$

$E_{cell}<1.1$ if $\frac{\left[Z{n}^{2+}\right]}{\left[C{u}^{2+}\right]}>1$