1 After each treatment, checking the hair and combing with a nit comb to remove nits and lice every 2â3 days may decrease the chance of selfâreinfestation. 2  Continue to check for 2â3 weeks to be sure all lice and nits are gone.
In chemistry, the molar mass M is a physical property defined as the mass of a given substance (chemical element or chemical compound) divided by the amount of substance. The base SI unit for molar mass is kg/mol. However, for historical reasons, molar masses are almost always expressed in g/mol.
Multiply the atomic weight of each element by the number of atoms of the element in the molecule, and add these to calculate the compound molar mass. In the example, the molar mass of Na2SO4 is (23 x 2) + (32 x 1) + (16 x 4) = 142 grams per mole.Divide the known mass of the compound by its molar mass to calculate the number of moles. For example, suppose the mass of your sample of Na2SO4 is 20 g. The number of moles equals 20 grams /142 grams/mole = 0.141 moles.Multiply the number of moles by the Avogadro constant, 6.022 x 10^23, to calculate the number of molecules in your sample.In the example, the number of molecules of Na2SO4 is 0.141 x 6.022 x 10^23, or 8.491 x 10^22 molecules of Na2SO4.n the example, the molar mass of Na2SO4 is (23 x 2) + (32 x 1) + (16 x 4) = 142 grams per mole. Divide the known mass of the compound by its molar mass to calculate the number of moles. For example, suppose the mass of your sample of Na2SO4 is 20 g. The number of moles equals 20 grams /142 grams/mole = 0.141 moles.