Which substance has hf defined as 0 kj/mol? h2o (s) ne (l) o2 (g) co2 (g)

O₂ (g).

Explanation:

All elements that found in nature has heat of formation (Hf) equal 0 J/mol.So, the substance that  has heat of formation (Hf) equal 0 J/mol is O₂ (g).H₂O is formed from the reaction of hydrogen and oxygen and has Hf, Also, the solidification of H₂O (s) from H₂O (l) has (Hf).Although, Ne (g) is found in nature and has no Hf, the liquification to form Ne (l) has heat of formation (Hf).CO₂ (g) is formed from the reaction between carbon and oxygen and so has heat of formation (Hf).

U whay do you need with?

60.0 - there are 3 significant numbers