Question

How much sulphuric acid can be obtained from 5 kg of pure sulphur?

Answer 1

Here,
Sulphuric acid is formed from sulphur by contact process. The reactions for the synthesis are as follows:
S + O2 →SO2
SO2 + ½ O2 → SO3
SO3 + H2SO4 → H2S2O7
H2S2O7 + H2O→ 2H2SO4

Starting from 1 mole of S, 2 moles of sulphuric acid are obtained.
As one mole of sulphuric acid is added as a reactant in step 3, the net synthesis is one mole of acid from one mole of S.

So, if the moles of S taken are determined, the moles of sulphuric acid formed would be known as well.

The number of moles of S in 5kg or 5000g
Moles = mass/atomic mass = 5000/32 = 156.25mol (atomic mass of S = 32u)
Moles of H2SO4 synthesized = 156.25mol
Mass of H2SO4, = mole H2SO4 × Molar mass H2SO4
= 156.25 × 98 (molar mass, M of H2SO4 is 98g/mol)
= 15312.5g or 15.31kg