Em tham khảo nha :
\(\begin{array}{l}
a)\\
CTHH:X{H_4}\\
{M_{X{H_4}}} = 4{M_{He}} = 16dvC\\
\Rightarrow {M_X} + 4{M_H} = 16\\
{M_X} = 16 - 4 = 12dvC\\
X:Cacbon(C)\\
b)\\
CTHH:C{H_4}\\
\% C = \dfrac{{12}}{{16}} \times 100 = 75\% \\
c)\\
C{H_4} + 2{O_2} \to C{O_2} + 2{H_2}O\\
{n_{C{H_4}}} = \dfrac{4}{{16}} = 0,25mol\\
{n_{C{O_2}}} = {n_{C{H_4}}} = 0,25mol\\
{V_{C{O_2}}} = 0,25 \times 22,4 = 5,6l
\end{array}\)