For the electrochemical cell, Mg(s)| Mg ^ 2+ (aq,1M)| | Cu ^ 2+...

For the electrochemical cell, \text{Mg(s)}\left|{\text{Mg}}^{\text{2+}} \left(\text{aq,1}\text{M}\right)\right|\left|{\text{Cu}}^{\text{2+}} \left(\text{aq,1}\text{M}\right)\right|\text{Cu}\left(\text{s}\right)$the$standard emf of the cell is \text{2}\text{.70 V}$at$\text{300 K}\text{.} When$the concentration o$f{\text{Mg}}^{\text{2+}}$is changed to$\text{x M,}$the cell potential changes to$\text{2}\text{.67 V}$at$\text{300 K}\text{.}$The$value of\text{x}is ________.<br /> <br /> (given,\dfrac{\text{F}}{\text{R}}{\text{=11500 K V}}^{- \text{1}} \text{,}where \text{F} is$the$Faraday constant and \text{R} is the gas constants,\text{ln}\left(\text{10}\right)\text{=}\text{2}\text{.30} )