Calculate the molar enthalpy of the reaction:

0.25 moles of a substance is reacted, and the heat released produces a 4.5°C temperature increase in 325 ml of water in a coffee cup calorimeter. (Recall that the specific heat capacity of water is 4.19 J/g°C.)
A) 24,511.5 J/mol
B) 35,733.8 J/mol
C) 44,321.9 J/mol
D) 57,422.2 J/mol

A

Explanation:

the old alchemists made significant contributions to science even though there starting premises were off a bit. their conclusions after failure would steer them into better directions for investigation. science is no more than close observation and the initial mistakes result in rethinking and retrying experiments.

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%