Question

how many moles of hydrogen are required to get 2 moles of HCL

Answer 1

Writing down the rough eqation of reactants giving products,we have-

H2+Cl2>HCl.

By general application of mathematical balancing,we get-

1/2H2+1/2Cl2>HCl.

If 1/2 mol H2 produces 1mol HCl,by application of quick analysis or long form unitary method,we reach at our conclusion that 1mol of hydrogen would be required.

A more critical edge can be given to this question which would more practically discuss limiting and excess reagents.

Hope it helps.