Ms. Wilson wrote:How do you convert 0.1 grams to millimoles?
You have to know the atomic or molecular weight of the substance. That is numerically equal to the molar mass in grams per mole.
If you know the chemical formula, look up the atomic weight of each element in the periodic table and add them all. Example H2O = 2 x 1 + 16 = 18, water is 18 g/mol.