Question

How many atoms of hydrogen are in 10.0g of H2O?

Answer 1

molar mass of H2O = 18.0 g/mol
number of mol of H2O = (mass of H2O)/(molar mass of H2O)
= 10.0/18.0
= 0.556 mole

1 mol of H2O has 2 mol of H
0.556 mol of H2O has (2*0.556) mol of H
0.556 mol of H2O has 1.11 mol of H

1 mol of Has (6.022*10^23) atom of H
1.11 mol of Has (1.11*6.022*10^23) atom of H
1.11 mol of Has (6.68*10^23) atom of H

Answer : (6.68*10^23)