What is the mass of 1.2 mol IrI3?

690 g IrI₃

Explanation:

To convert from moles to grams, you have to use the molar mass of the compound. The molar mass of IrI₃ is 572.92 g/mol. You use this as the unit converter in this equation:

Round to the lowest number of significant figures which is 2 to get 690 g IrI₃.

2.345 moles

Explanation:

From the stoichiometry of the formula, Na₂Cr₂O₇

It is clear that the 1 mole of sodium dichromate contains 2 moles of sodium, 2 moles of chromium and 7 moles of oxygen.

Thus, given that the compound contains 0.67 moles of sodium. Thus, applying unitary method as:

2 moles of sodium and 7 moles of oxygen are present in 1 mole of sodium dichromate.

Also,

1 mole of sodium and 7/2 moles of oxygen are present in 1/2 moles of sodium dichromate.

Thus,

0.67 moles of sodium and (7/2)*0.67 moles of oxygen are present in (1/2)*0.67 moles of sodium dichromate.

0.67 moles of sodium and 2.345 moles of oxygen are present in 0.335 moles of sodium dichromate.

So, moles of oxygen present = 2.345 moles