The product of the additional reaction of one mole of acetylene with 1 mol of H2O is..

The reaction of one mole of acetylene (C2H2) with one mole of water (H2O) in the presence of a suitable catalyst (such as HgSO4 and H2SO4) will result in the formation of acetaldehyde (CH3CHO). This is a hydration reaction, specifically a hydroboration-oxidation reaction.

Here is the step-by-step process:

1. Acetylene (C2H2) reacts with water (H2O) in the presence of HgSO4 and H2SO4 as catalysts.
2. The water molecule adds across the triple bond of the acetylene.
3. The reaction follows Markovnikov's rule, where the hydrogen (H) from water attaches to the carbon in the acetylene that has more hydrogen atoms, and the hydroxyl group (OH) attaches to the other carbon.
4. This results in the formation of acetaldehyde (CH3CHO).

So, the product of the additional reaction of one mole of acetylene with 1 mol of H2O is one mole of acetaldehyde.