Identify W, X, the overall reaction, and the voltmeter reading in a Zinc-copper cell with given standard electrode potentials.

In a Zinc-copper cell, Zinc has a more negative standard electrode potential ($-0.76 \text{ V}$) compared to copper ($+0.34 \text{ V}$). This means Zinc is more easily oxidized and acts as the anode (negative electrode). The electrode labeled W is on the left, typically representing the anode.
The identity of W is $\boxed{\text{Zinc (Zn)}}$.

Since W is the Zinc electrode, X must be the other electrode, which is copper. Copper acts as the cathode (positive electrode) where reduction occurs.
The identity of X is $\boxed{\text{Copper (Cu)}}$.

The reading on the voltmeter is the standard cell potential ($E^\circ_{cell}$).

Here, $E^\circ_{cathode}$ is the standard reduction potential of copper ($+0.34 \text{ V}$), and $E^\circ_{anode}$ is the standard reduction potential of zinc ($-0.76 \text{ V}$).