\(P=\frac{x+3y}{3x+y}.\frac{4x-2y}{x-y}-\frac{x+3y}{3x+y}.\frac{x-3y}{x-y}\)

\(=\frac{x+3y}{3x+y}\left(\frac{4x-2y}{x-y}-\frac{x-3y}{x-y}\right)\)

\(=\frac{x+3y}{3x+y}.\frac{3x+y}{x-y}=\frac{x+3y}{x-y}\)

1. PTHH: 4P + 5O₂ \(\rightarrow\) 2P₂O₅

2. \(n_P=\frac{3,1}{31}=0,1\left(mol\right)\)

Từ PT \(\Rightarrow\) \(n_{O_2}=0,125\left(mol\right);n_{P_2O_5}=0,05\left(mol\right)\)

đktc: \(V_{O_2}=0,125.22,4=2,8\left(l\right)\)

3. \(m_{P_2O_5}=0,05.142=7,1\left(g\right)\)