Question

Determine the formula weight, number of molecule and number of moles

1). 1.7293 x10^16 Molecules of H2O

2). 5.699 g of BaSO4

Answer 1

1.) formula weight of H₂O = 2(atomic weight of H) + ( atomic weight of O) = 2(1.00794) + (15.9994) = 18.01528 u

no. of molecule of H₂O = 1.7293 10¹⁶ molecule

no. of mole of H₂O = 1 mole of any substance contain 6.022 10²³ molecule then 1.7293 10¹⁶ molecule =

1.7293 10¹⁶ / 6.022 10²³ = 2.8716 10^-8 mole.

2.) Formula weight of BaSO₄ = (atomic weight of Ba) + (atomic weight of S) + 4(atomic weight of O)

= (137.327) + (32.065) + 4(15.9994) = 233.3896 u

No. of mole of BaSO₄ = 5.699/233.3896 = 0.0244183 mole

No. of molecule of BaSO₄ = 1 mole contain 6.022 10²³ molecule then 0.0244183 mole contain

6.022 10²³ 0.0244183 = 1.47 10²² molecule.