1) how many molecules are present in 1.5 moles of NaCl?

2) how many atoms of chlorine are in 19.0 grams of MgCl2?

1 answer

1 mole of anything contains 6.02E23 molecules.

Convert 19.0 g MgCl2 to mols. mol = grams/molar mass. Then convert that many mols to molecules MgCl2 (use #1 as a template if needed). Then you notice there are 3 atoms for each molecule so 3x molecules gives you atoms.