The electrode potential for Mg electrode varies according to the equation

\(E_{Mg^{2+}/Mg}\ = \ E_{Mg^{2+}/Mg}^{o} \ - \ \frac{0.059}{2}log\frac{1}{[Mg^{2+}]}\) 

The graph of EMg2+ / Mg vs log [Mg2+] among the following is:

1.    2.  
3.    4.  
HINT: Compare equation with y=c + (-mx)
Explanation: 
 
Electrode potential for Mg electrode varies according to the equation -
EMg2+/Mg=E°Mg2+/Mg-0.0592log1Mg2+EMg2+/Mg=E°Mg2+/Mg+0.0592logMg2+EMg2+/Mg=0.0592logMg2++E°Mg2+/Mg
This equation represents equation of straight line. It can be correlated as
EMg2+/MgY= 0.0592M  log  Mg2+X + E°Mg2+/Mg+C
So, intercept (C) = EMg2+ / Mg
Thus, equation can be diagramatically represented as