Question

How many moles of hydrogen are there in 0.925g of ca(oh)2?

Answer 1

(0.925 g Ca(OH)2) / (74.0927 g Ca(OH)2/mol) x (2 mol H / 1 mol Ca(OH)2) = 0.0250 mol H atoms

(If you need moles of H2 molecules, divide the answer above by 2.)