Key: 3. (Try this without a calculator) If the ΔH° (delta H°) for the reaction 2HF(g) = H 2 (g) + F 2 (g) is 550 kJ, what is ΔH° f (delta H° f ) for HF? a. 550 kJ b. -550 kJ c. 275 kJ d. -275 kJ e. 1100 kJ f. -1100 kJ First lets refresh our understanding of what heat of formation (ΔH° f ) is. It is the energy required to form one mole of a certain molecule from elements in their standard state. This problem simply gives us the reaction which relates to the enthalpy of formation of HF but in reverse and with the wrong coefficients. The first step should be to write out the reaction representing the formation of 1 mol of HF:
This is the end of the preview.
access the rest of the document.