\(\begin{array} c&{3CH\equiv CH} &\rightleftharpoons &{C_6H_6}\\t = 0&1&&0\\{t=t}&1-\alpha&&\frac \alpha3
\end{array}
\)
\(m_{mix} =\frac{M_{CH \equiv CH} \times n_{CH\equiv CH} + M_{C_6H_6} \times n_{C_6H_6}}{n_{CH\equiv CH} + n_{C_6H_6} }\)
\(50 = \frac{26 (1 - \alpha) + 78(\frac \alpha 3)}{1 - \alpha + \frac\alpha 3}\)
\(\Rightarrow 50 (1 - \frac{2\alpha}3)= 26\)
\(\Rightarrow \alpha = \frac{72}{100} = 0.72\)
