1. Note the amounts of atoms of all the component in HNO3, which are 1 atom of Hydrogen, 1 atom of Nitrogen and 3 atoms of Oxygen. Multiply each of the atomic weights by the amount of atoms of each element contained in the compound. Add up the results to obtain the molar mass: 1 + 14 + (16 x 3) = 63 gr/mole.
2. In one molecule of sodium sulfate, or Na2 SO4, there are seven atoms in all.
3. Magnesium dichloride is a magnesium salt comprising of two chlorine atoms bound to a magnesium atom. It is a magnesium salt, an inorganic chloride and a magnesium halide.