Four equations featuring enthalpy changes are given. $\text{Na(g)} \rightarrow \text{Na}^+(\text{g}) + e^- \quad \Delta H = W$ $\text{Na(g)} \rightarrow \text{Na}^{2+}(\text{g}) + 2e^- \quad \Delta H = X$ $\text{Na(s)} \rightarrow \text{Na(g)} \quad \Delta H = Y$ $\text{Na(s)} \rightarrow \text{Na}^{2+}(\text{g}) + 2e^- \quad \Delta H = Z$ Which one corresponds to the second ionisation energy of sodium?
- A$2W$
- B$X - W$
- C$Y - W$
- D$Z - Y$