Damage per second and damage per shot are related but distinct.
A lvl2 mortar you describe has 5damage/second, and since they fire every 5 seconds, they have 5/(1/5)=25 damage/shot. Similarly for all other units.
CoC wikia has both damage/second and damage/shot listed for all items.
Be careful to use the appropriate metric in gauging a unit however; in general damage/shot is more useful for an aggregate idea of overall 'damage dealing'.