Chapter 18, Problem 18.101QP

The magnitudes (but not the signs) of the standard reduction potentials of two metals X and Y are

$\begin{array}{l}{\text{Y}}^{2+}+2e^{-}\to \text{Y }|E°|\text{= 0}\text{.34 V}\\ {\text{X}}^{2+}+2e^{-}\to \text{X }|E°|\text{= 0}\text{.25 V}\end{array}$

where the || notation denotes that only the magnitude (but not the sign) of the E° value is shown. When the half-cells of X and Y are connected, electrons flow from X to Y. When X is connected to a SHE, electrons flow from X to SHE. (a) Are the E° values of the half-reactions positive or negative? (b) What is the standard emf of a cell made up of X and Y?