The acid power of carboxylic acids depends on the electron displacement properties of group R. If group R has the property of displacing electrons on its own, then this acid will be a strong acid.

If group R has the property of displacing electrons from the other side, this acid will be a weak acid. The +I effect of H, CH_{3}, C_{2}H_{5} and C_{3}H_{7} groups increases in this sequence.

Therefore, the ability of these groups to displace electrons from themselves increases in this order. Therefore, the decreasing order of acid power of these acids is also the same.