Ammonia nh3 is used as a refrigerant. at its boiling point of -33, the standard enthalpy of vaporization of ammonia is 23.3 kj/mol. how much heat is released when 50.0 g of ammonia is condensed

Answer is:  68.385 kJ heat is released when ammonia is condensed.

m(NH₃) = 50.0 g.

n(NH₃) = m(NH₃) ÷ M(NH₃).

M(NH₃) = Ar(N) + 3Ar(H) · g/mol.

M(NH₃) = 14 + 3.031 · g/mol = 17 g/mol.
n(NH₃) = 50.0 g ÷ 17.031 g/mol.
n(NH₃) = 2.935 mol; amount of ammonia.
Hvap = 23.3 kJ/mol; the heat of vaporization for ammonia.
Q = Hvap · n(NH₃).
Q = 23.3 kJ/mol · 2.935 mol; energy.
Q = 68.385 kJ.

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.