How many molecules are present in 2.1 mol of sulfuric acid H2SO4?

Answer 1

Moles is a measure of how many molecules something has, and it has nothing to do with the chemical composition. One mole is one Avogadro's number of molecules, i.e. about 6.022 x 1023, so 2.1 moles (yes, mol is the symbol) would be about 1.2646 x 1024 molecules.

If, on the other hand, you are talking about mass, then you need to consider the atomic masses of each of the components. H2SO4 has a mass of (2 x 1.00794) + (1 x 32.065) + (4 x 15.9994) g mol-1 which adds up to 98.07848 g mol-1, so 2.1 moles is 205.964808 g.