Question

This is the chemical formula for talc (the main ingredient in talcum powder): mg3(si2o5)2(oh)2. an analytical chemist fins that there are 6.10 moles of magnesium in a sample of talc, how many moles of oxygen are in the sample?

Answer 1

In one mole of talc, we observe that there are:
3 moles of Mg
4 moles of Si
2 moles of H
12 moles of O

The molar ratio of O to Mg is then:

12 moles of O : 3 moles of Mg = 4 : 1

Therefore, if 6.1 moles of Mg are present, the moles of O are:

4 * 6.1 = 24.4 moles of O