Heat of formation in general can be positive negative and zero
✔️ According to IUPAC heat of formation of elements in it's stable form(standard state) is zero.
✔️ Generally heat of formation is negative but for a unstable product the heat of formation is positive
Trick:
🔥 ∆Hf for stable product is negative
🔥∆Hf for unstable product is positive
🔥∆Hf for elements in its standard state is zero
✔️For the second question its mentioned heat of formation of compounds
So answer will be positive and negative
✔️ According to IUPAC heat of formation of elements in it's stable form(standard state) is zero.
✔️ Generally heat of formation is negative but for a unstable product the heat of formation is positive
Trick:
🔥 ∆Hf for stable product is negative
🔥∆Hf for unstable product is positive
🔥∆Hf for elements in its standard state is zero
✔️For the second question its mentioned heat of formation of compounds
So answer will be positive and negative