Group 1a elements have electron(s) in their valence shell.
a. 1
b. 2
c. 4
d. 8

a. 1

Explanation:

As you know the group 1A elements are also called the Alkali metals and are highly reactive metals because they have only one electron in their valence shell, this means that all prior levels are full and stable, and they have only one electron in the upper level of the valence shell and it is ready to react with any element that is close to it.

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%

practical process described pest part of scientific investigation.

because practical knowledge is powerful then therotical knowledge.