Question

What will happen if there is no effective collision and low activation energy of reactants?

Answer 1

Reaction doesn't occur

Explanation:

If there is no successful collision and low activation energy reaction doesn't happen. If particles don't collide bonds don't break.
I don't know if you know this, in order for particles to react they must collide with the correct orientation and sufficient energy. If there is no low activation energy or energy input the reaction doesn't start at all.