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)

On the left (reactant) side you have 6 N-H bonds and 1 Cl-Cl bond 
On the right (product) side you have 4 N-H bonds, 1 N-N bond and 2 H-Cl bonds 

Add up the bond energies for each side (multiplying by the number of bonds) and calculate the difference for your ΔHº