What is true about exothermic reactions? a. more heat is given off than is put into the reaction. b energy from an outside source is continuously being added. c. the reaction container always feels cold. d. the reactants have more energy than the products.

A. More heat is given off than is put into the reaction

Think of the word "exo" and then think of how the reaction exerts the energy into the reaction. Then "thermic" which can be easily identified with heat

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%