could the finches that evolved
bigger beaks in this study evolve
smaller beaks some day?

Yes

Explanation:

Natural selection allows for the survival of the fittest. According to natural selection, those organisms are able to live and reproduce which have better traits to adapt to an environment. Hence, in the future, if conditions become favourable for small finches then through evolution, small finches will be seen widely again. If the food sources gain become favourable for small finches, then the birds with small finches will live and reproduce more

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%