question_answer 23)

What is the mass of (a) 0.2 mole of oxygen atoms? (b) 0.5 mole of water molecules?  

Answer:

(a) Mass of 1 mole of oxygen atom = 16 u Mass of 0.2 mole of oxygen atoms = (16 x 0.2) u = 3.2 u  (b) Mass of 1 mole of H2O molecule = (1 x 2 + 16) = 18 u Mass of 0.5 mole of H2O molecule = (18 x 0.5) u =9 u.