a) \(4P+5O2-->2P2O5\)
\(n_P=\frac{24,8}{31}=0,8\left(mol\right)\)
\(n_{O2}=\frac{34}{32}=1,0625\left(mol\right)\)
\(n_P\left(\frac{0,8}{4}\right)< n_{O2}\left(\frac{1,0625}{5}\right)\Rightarrow O2dư\)
\(n_{O2}=\frac{5}{4}n_P=1\left(mol\right)\)
\(n_{O2}dư=1,0625-1=0,0625\left(mol\right)\)
\(m_{O2}dư=0,0625.32=2\left(g\right)\)
b) \(n_{P2O5}=\frac{1}{2}n_P=0,4\left(mol\right)\)
\(m_{P2O5}=0,4.142=56,8\left(g\right)\)