2co3+(aq)+2cl−(aq)→2co2+(aq)+cl2(g) . e∘=0.483 v what is the cell potential at 25 ∘c if the concentrations are [co3+]= 0.717 m , [co2+]= 0.363 m , and [cl−]= 0.152 m and the pressure of cl2 is pcl2= 3.40 atm ?

Look for Q. The equation you would use to find Q would be - [Co2+] ^2 [PCl2] / [Co3+] ^2 [Cl-]^2 
then plug in the the numbers you are given into the equation [0.363 M]^2 [3.40 atm] / [0.717 M] ^2 [0.152] ^2 0.4480 / 0.0119 = 37.7183 
Next you would want to determine the value of n = 2 
then you will want to plug in the values you have to the final equation E=E∘−(0.0591(n))logQ 
E =0.71 - (0.0591(2)) * log 37.7
E= 0.71 - 0.02955 * 1.58 
E= 0.71 – 0.0467
E= 0.6633

Ithink the answer is 56.

The correct answer is d