Use the data in the table above to calculate an approximate ΔH∘ in kilojoules for the synthesis of hydrazine from ammonia:

2NH3 (g) + Cl2 (g) ⟶N2H4 (g) + 2HCl (g)

Express your answer to two significant figures and include the appropriate units.

Hi, I just researched for the data since you forgot to present it: These are the standard enthalpies of formation:

NH3 (g) : - 45.9 kJ/mol

N2H4 (g) : + 95.4 kJ/mol

HCl (g) : - 92.3 kJ/mol

We use Hess's law to find the the deltaH of the reaction.

ΔHrxn = ∑ (v * standard heat of formation of products) - ∑ (v * standard heat of formation of reactants)

where v is the coefficient found in the balanced reaction. The heat of formation of diatomic molecules is zero. Thus,

ΔHrxn = (+95.4 + 2*-92.3) - (2*-45.9)

ΔHrxn = + 2.6 kJ/mol