The sum of all percent abundances for magnesium is equal to 100. explain why this is reasonable.

All magnesium is divided in abundances.

Explanation:

So the amount of magnesium that exists in the planet is finite, we have a 100% of magnesium, now as you know there are different isotopes that exists and when you divide that 100% in the different isotopes. it is logical that the sum of all the different abundances of magnesium is equal to the initial 100%.

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%

fe 55.85 g/mol and h2o 18.02 g/mol.