Solution
= Solution
Equality of <chemical potentials> gives $d\mu_{\rm l}=d\mu_{\rm g}$ along coexistence. Since
$$
d\mu=-s\,dT+v\,dp,
$$
one obtains
$$
(v_{\rm g}-v_{\rm l})\frac{dp}{dT}=s_{\rm g}-s_{\rm l}.
$$
Using $L=T(s_{\rm g}-s_{\rm l})$ gives the <Clausius-Clapeyron relation>
$$
\boxed{\frac{dp}{dT}=\frac{L}{T(v_{\rm g}-v_{\rm l})}.}
$$