Reaction Energy Profile

measured

Eₐ forward132 kJ/mol

ΔH reaction−226 kJ/mol

Temperature500 K

Drag the ‡ marker or the product level on the chart to reshape the profile directly.

No common catalyst for this one. It is a single elementary step, so there is one activated complex and nothing to route around.

ΔH from ΔH°f (NIST). Eₐ = 132 kJ/mol, measured above ~500 K.

▼Exothermicreleases 226 kJ/mol; products sit below the reactants

Eₐ forward132 kJ/mol

Eₐ reverse358 kJ/mol

ΔH, overall change−226 kJ/mol

ΔH = Eₐ(fwd) − Eₐ(rev)−226 = 132 − 358

‡ One O is half-bonded to nitrogen and half-bonded to carbon at the same instant.

Fraction past Eₐ, forward1.6 × 10^-14

Fraction past Eₐ, reverse4.0 × 10^-38

The forward barrier is 226 kJ/mol lower, so at 500 K the forward direction wins.

The x-axis is the reaction coordinate, the path from reactants to products. Not time.

Eₐ is measured up from a flat level, never from the axis.

ΔH is the gap between the two flat levels. Peak height never changes it.

Transition state: a maximum. Bonds half-broken and half-formed. Cannot be isolated.

Intermediate: a minimum between two peaks. A real species, and detectable.

Raising T does not lower Eₐ. It pushes more collisions past the same barrier.

A collision also needs the right orientation, not just enough energy.

A catalyst opens a different path with a lower barrier, then is regenerated. ΔH is untouched.

Peroxide releases 196 kJ/mol and still keeps for months. A high Eₐ means kinetic control.