# The standard reaction potential $\in ^0$ for the half reaction are: $Zn \to Zn^{2+}+2e^{-}; \in^0 =0.76\;V; Cu \to Cu^{2+}+2e^{-} ;\in ^0 =0.34\;V$ The emf for the cell reach ,$2n(r) +cu^{2+}\to Zn^{2+}+Cu(r)$
$\begin{array}{1 1} 0.42\;V \\ -0.42 \;V \\ -1.1\;V \\+1.1\;V \end{array}$