Question

1. Calculate the formula mass for BaSO4 2. What is the percent by mass of oxygen in sodium nitrate?

Answer 1

1. Formula mass of BaSO₄ = (atomic mass of barium + atomic mass of sulphur + atomic mass of four oxygen atom)

= {137.327 + 32.065 + (15.999 * 4)}

= 233.388 g/mole

2. Formula of sodium nitrate is NaNO₃

Molar mass of sodium nitrate = {23 + 14 + (16*3)} = 85 g/mole.

Therefore, in 85 gm sodium nitrate there is 48 g oxygen present by mass.

Percentage of oxygen present by mass in NaNO₃ is

= (48 * 100) / 85

= 56.47 %