En una reacción química se produjeron 5.02 x 1023 moléculas de ZnO. ¿A cuántos gramos corresponde esta cantidad de moléculas?

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

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%