🤓 Based on our data, we think this question is relevant for Professor Cruickshank's class at NAU.
Which of the following substances have a standard heat of formation (ΔH f°) of zero?
i) Cl2(g) at 2 atm
ii) C2H6 at standard conditions
iii) O2(g) at 25.0 °C
iv) 1 atm Fe at 1200 °C
Recall that substances with standard heat of formation of zero are the ones in their natural state at 1 atm.
Analyzing the choices: