For the reaction, 2cr2+ + cl2(g) > 2cr3+ + 2cl- e cell (standard conditions) = 1.78v calculate ecell (standard conditions) for the related reaction cr3+ + cl- > cr2+ + 1/2cl2(g)
a. 0.89 v
b. - 0.89 v
c. 1.78 v
d. - 1.78 v
e. non of these

-1.78 V

Explanation:

There are several rules required to calculate the cell potential:

given standard cell potential, we may reverse the equation: the products of a given reaction become our reactants, while reactants become our products in the reversed equation. For a reversed equation, we change the sign of the cell potential to the opposite sign;if we multiply the whole equation by some number, this doesn't influence the cell potential value. It only produces a different expression in the equilibrium constant.

That said, notice that the initial reaction with respect to the final reaction is:

reversed: chromium(III) cation and chloride anion become our reactants as opposed to the products in the initial reaction, so we change the sign of the cell potential to a negative value of -1.78 V;each coefficient is multiplied by a fraction of . It doesn't influence the value of the cell potential.

Thus, we have a cell of E = -1.78 V.