1) $4Fe{S}^2+11O^2\underrightarrow{t^o}2F{e}^2{O}^3+8S{O}^2$

(2) $2S{O}^2+O^2\stackrel{{}^{V^2{O}^5}}{\to }2S{O}^3$

(3) $nS{O}^3+H^{2}S{O}^4\to H^{2}S{O}^4.nS{O}^3$

(4) $H^{2}S{O}^4.nS{O}^3+n{H}^{2}O\to \left(n+1\right)H^{2}S{O}^4$

Gọi CTPT của X là C_xH_yO_z.

x:y:z=$\frac{40\%}{12}:\frac{6,67\%}{1}:\frac{53,33\%}{16}$=1:2:1.

CTPT của X là (CH₂O)_n, mà M_X=60 g/mol. Suy ra X là C₂H₄O₂.

(1) $4Fe{S}^2+11O^2\underrightarrow{t^o}2F{e}^2{O}^3+8S{O}^2$

(2) $2S{O}^2+O^2\stackrel{{}^{V^2{O}^5}}{\to }2S{O}^3$

(3) $nS{O}^3+H^{2}S{O}^4\to H^{2}S{O}^4.nS{O}^3$

(4) $H^{2}S{O}^4.nS{O}^3+n{H}^{2}O\to \left(n+1\right)H^{2}S{O}^4$