`M_{X}=7,25.2=14,5(g//mol)`
`->\frac{26x+28y+2z}{x+y+z}=14,5`
`->11,5x+13,5y-12,5z=0`
`->m_{X}=0,1.14,5=1,45(g)`
`n_{C}=0,1(mol)`
`->2x+2y=0,1(2)`
`m_{C}=0,1.12=1,2(g)`
`->m_{H}=1,45-1,2=0,25(g)`
`2x+4y+2z=0,25(3)`
Từ `(1),(2),(3)` giải hệ phương trình
$\to \begin{cases}x=0,025(mol)\\y=0,025(mol)\\z=0,05(mol)\\\end{cases}$
`->%V_{C_2H_2}=\frac{0,025}{0,1}.100=25%`