1. How many molecules are in 3.00 moles of H.0?

1.8 ⋅ 10 24  molecules

Explanation:

As you know, a mole is simply a very, very large collection of molecules.

In order to have one mole of a molecular substance, you need to have  

6.022

⋅

10

23

molecules of that substance  

→

this is known as Avogadro's number and it can be used as a conversion factor to go from number of molecules to moles and vice versa.

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explanation:

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%