An unknown gas, X2(g), which behaves much like N2(g), is analysed and the following enthalpies of formation are obtained;
Gas delta(Hf)
X(g) 401 kJ/mol
H(g) 216 kJ/mol
X2H4(g) 413 kJ/mol
We also know that the X-H bond energy is 284 kJ/mol. Use this information to estimate the X-X single-bond energy. (ans in kJ/mol.)
Not sure how to figure this out.