calculate the standard free-energy change for the synthesis of hydrazine from nitrogen and hydrogen.

Question

N2(g) + H2(g) right arrow N2H4(l)

Answer 1

N2 + 2H2 ==> N2H4

dGrxn = (n*dGf products) - (n*dGf reactants).
According to my tables N2H4 is -16 kJ/mol, N2 and H2 are zero.
You need to use the numbers in your tables.