1 mole of NH42SO4 contains 42 moles of H. We take the 42 moles of H and multiply that times Avogadro's number (6.02x10^23) and get 2.5284x10^25 atoms of hydrogen
He was brought to be believe that the earth was geocentric, meaning the earth was centered and everything orbited around it but he then published his work saying that is was heliocentric. So in the end believed in heliocentric. Let me know if this helped.
Moles= molarity x liter
=0.2500 M x 0.500 L
= 0.1250 mol
mass C2H2O4 . 2H2O = 0.1250 mol x (126.068 g / 1 mol)
=15.76 g