Is there a relationship between density of a substance and it's solubility in water

There is no direct relationship between solubility and density. Density is the ratio of the substance's mass to its volume. On the other hand, solubility is the maximum amount of solute that a solvent could take to make a saturated solution. They are both temperature-dependent, but they don't affect each other.

67.6g

Explanation:

Given parameters:

Number of molecules  = 5.02 x 10²³molecules

Unknown:

Mass of ZnO  = ?

Solution;

To solve this problem, we convert the given molecules to number of moles first.

        6.02 x 10²³ molecules is contained in 1 mole of a substance

         5.02 x 10²³ molecules will contain   = 0.83mole of ZnO

Now;

  Mass of ZnO  = number of moles x molar mass

        Molar mass of ZnO  = 65.4 + 16  = 81.4g/mol

Mass of ZnO  = 0.83 x 81.4  = 67.6g