我想問f.5 CHEM 的CONTACT PROCESS

Step 1: making SO2
method a: burning sulphur in air directly: S(s)+O2(g) =heating= SO2(g)
method b: burning metal sulphate:

Step 2: making SO3
method: heating SO2
SO2(g)+O2(g) =(high temperature, high pressure)= SO3(g)

Step 3: making oleum(H2S2O7)
mathod: adding SO3 into H2SO4
SO3(g)+H2SO4(l) === H2S2O7(l)

Step $: making H2SO4
mathod: add water into H2S2O7(l)
H2S2O7(l)+H2O(l) == H2SO4(aq)