Consider the following reaction: a2 + b2 → 2ab δh = –321 kj bond energy (a2) = 1/2ab bond energy (b2) =393 kj/mol. what is the numerical value for bond energy (a2) ?

The numerical value for Bond energy of is -238 kJ/mol

Explanation:

The balanced chemical reaction is,

The expression for enthalpy change is,

where,

n = number of moles

If    

Now put all the given values in this expression, we get

Therefore, the bond energy of is -238 kJ/mol

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%