Calculate the volume of hydrogen, in L, produced when 12.15 g of magnesium react completely with water. Assume S..T.P.

Answer 1

Mg + H2O ==> MgO + H2
mols Mg = 12.15/atomic mass Mg
Convert mols Mg to mols H2 using the coefficients in the balanced equation.
Now convert mols H2 to L remembering that 1 mol of any gas occupies 22.4L at STP