Question

A compound made of two elements, iridium (Ir) and oxygen (O), was produced in a lab by heating iridium while exposed to air. The following data was collected:

Mass of crucible: 38.26 g
Mass of crucible and iridium: 39.52 g
Mass of crucible and iridium oxide: 39.73 g

Show, or explain, your calculations as you determine the empirical formula of the compound.

Answer 1

mass of iridium = 1.26
mass of iridium oxide = 1.47

molar mass of iridium = 192g/mol
molar mass of oxygen = 16 g/mol

as of yet we do not the ratio of Ir to O in the formula a iridium oxide \[Ir _{x}O _{y}\]...

Answer 2

mass of oxygen = 0.21g

dividing the measured mass by the molar mass for each element

for Ir; 1.26g / 192g/mol = ~ 0.0066mol

for O; 0.21g / 16g/mol = ~0.013mol

The ratio of moles of
Ir:O
= 0.0066:0.013
= 6.6:13
~1:2

Hence \[IrO _{2}\]