Penurunan Tekanan Uap Jenuh

(A)   Fraksi mol urea

\begin{equation*}
\begin{split}
X_{\text{urea}} & = \frac{n_{\text{urea}}}{n_{\text{urea}} + n_{\text{air}}} \\\\
X_{\text{urea}} & = \frac{\dfrac{6}{60}}{\dfrac{6}{60} + \dfrac{54}{18}} \\\\
X_{\text{urea}} & = \frac{0,1}{0,1 + 3} \\\\
X_{\text{urea}} & = \frac{0,1}{3,1} \\\\
X_{\text{urea}} & = \frac{1}{31}
\end{split}
\end{equation*}

(B)   Penurunan tekanan uap

\begin{equation*}
\begin{split}
\Delta P & = X \:.\: P^o \\\\
\Delta P & = \frac{1}{31} \:.\: 31 \\\\
\Delta P & = 1 \text{ mmHg}
\end{split}
\end{equation*}

(C)   Tekanan uap larutan

\begin{equation*}
\begin{split}
P & = P^o - \Delta P \\\\
P & = 31 - 1 \\\\
P & = 30 \text{ mmHg}
\end{split}
\end{equation*}