Collision Theory, Activation Energy and Catalysts

What makes a collision effective

Two requirements: enough energy to reach the activation barrier, and correct orientation. Most collisions fail on one or the other.

Raising temperature works far better than you would guess from average speeds alone: it shifts the whole distribution so that a much larger fraction of molecules exceed $E_a$. A $10°$C rise often doubles the rate.

Catalysts

A catalyst provides an alternative pathway with a lower $E_a$. It is not consumed, and — crucially — it does not change $\Delta H$, the position of equilibrium, or the relative energies of reactants and products.

It speeds up the forward and reverse reactions by the same factor, which is exactly why equilibrium position is unaffected.