Carbon reacts with oxygen to produce carbon dioxide (CO2(g), AHF = -393.5 kJ/mol) according to the equation below. C(s) +202 (g) → CO2(g)
What is the enthalpy change of the reaction?
Use AHxn-E (AHg products) -(AHe reactan te).
--393.5 kJ
-196.8 kJ
196.8 kJ
393.5 kJ

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%

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