Iron(iii) oxide is formed when iron combines with oxygen in the air. how many grams of fe2o3 are formed when 25.9 g of fe reacts completely with oxygen? 4fe(s) + 3o2(g) > 2fe2o3(s)

a.12.0g b. 25.0g c. 37.0g d. 49.0g

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%