\(\begin{array}{l}
2)\\
{C_3}{H_8} + 5{O_2} \to 3C{O_2} + 4{H_2}O\\
{C_2}{H_4} + 3{O_2} \to 2C{O_2} + 2{H_2}O\\
3)\\
a)\\
{C_2}{H_4} + 3{O_2} \to 2C{O_2} + 2{H_2}O\\
b)\\
n{C_2}{H_4} = \dfrac{{11,2}}{{22,4}} = 0,5\,mol\\
n{O_2} = 3 \times 0,5 = 1,5\,mol\\
V{O_2} = 1,5 \times 22,4 = 33,6l\\
c)\\
Vkk = V{O_2} \times 5 = 168l
\end{array}\)