The diameter of an average size penny was found to be 1.95 cm. which digit in the diameter of the penny represents the estimated digit? a 1 b 9 c 5

- C) 5

Explanations:- The ending digit of a number is always estimated digit as the actual value might be slightly lower or greater than the estimated value. So, in measurements we record the results with one estimated digit that is uncertain digit.

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%