Which is an important principle to follow when studying climates? a. plants that need certain conditions to thrive today needed those same basic conditions in the past. b. the weather on any given day can provide all the necessary information to determine the climate of a region. c. climates can only exist in areas where human development is minimal. d. climates will always slowly change over time.

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%

in the analysis of systems that involve fluid flow, we frequently encounter the combination of properties u and pv.