Question: can an alkene have the same formula as a cycloalkane

Answer: Yes, The cycloalkanes without side chains are classified as small (cyclopropane and cyclobutane), common (cyclopentane, cyclohexane, and cycloheptane), medium (cyclooctane through cyclotridecane), and large (all the rest). Each is an isomer of its alkene counterpart--for example, cyclopropane has the same chemical formula (CH) as propene.