How to calculate the electromotive force of a silver chloride/ silver bromide cell?
$$\begin{align}
E_{\ce{Ag/AgBr}}&amp;=E_{\ce{Ag/Ag+}}^{\circ}+0.059\log\frac{K_{\rm sp, AgBr}}{[\ce{Br-}]} \\
E_{\ce{Ag/AgCl}}&amp;=E_{\ce{Ag/Ag+}}^{\circ}+0.059\log\frac{K_{\rm sp, AgCl}}{[\ce{Cl-}]} \\
EMF&amp;=0.059 \cdot \left| \log \left( {\frac  
{ K_{\rm sp, AgCl} \cdot [\ce{Br-}]}
{ K_{\rm sp, AgBr} \cdot [\ce{Cl-}]}
} \right) \right| \\
EMF&amp;=0.059 \cdot \left| \log \left( {\frac  
{ 2.8\times10^{-10} \cdot 0.001}
{ 3.3\times10^{-13} \cdot 0.2}
} \right) \right| \\
EMF&amp;=0.059 \cdot \left| \log \left( {\frac { 2.8}{ 0.66} } \right) \right| \\
EMF&amp;=0.037 \rm \ V\\
\end{align}$$