2Al(OH)3 + 3H2SO4 → Al2(SO4)3 + 6H2O
\(n_{Al\left(OH\right)_3}=\frac{78}{78}=1\left(mol\right)\)
a) Theo PT: \(n_{H_2SO_4}=\frac{3}{2}n_{Al\left(OH\right)_3}=\frac{3}{2}\times1=1,5\left(mol\right)\)
\(\Rightarrow m_{H_2SO_4}=1,5\times98=147\left(g\right)\)
b) Theo PT: \(n_{Al_2\left(SO_4\right)_3}=\frac{1}{2}n_{Al\left(OH\right)_3}=\frac{1}{2}\times1=0,5\left(mol\right)\)
\(\Rightarrow m_{Al_2\left(SO_4\right)_3}=0,5\times342=171\left(g\right)\)