Formula from Chapter 9: definition of mole fraction

\(X_{\mathrm{A}} = \dfrac{n_{\mathrm{A}}}{n_{\mathrm{total}}}\)     

\(n_{\mathrm{\ce{N2}}}\) \(= 4.0\ \mathrm{mol}\)


\(n_{\mathrm{total}}\) \(= 5.0\ \mathrm{mol}\)


\(X_{\mathrm{\ce{N2}}}\) \(= \dfrac{n_{\mathrm{\ce{N2}}}}{n_{\mathrm{total}}}\)

\(\ \ \ =\dfrac{4.0\ \mathrm{mol}}{5.0\ \mathrm{mol}}\)

\(\ \ \ =0.80\)