How many different alkenes can be hydrogenated to form hexane?

Hint: Alkenes are those carbon chains in which a double bond is present. Hexane is a compound of the alkane group and it is the sixth compound because of its six carbon atoms chain. Hydrogenation is a process in which there is the addition of hydrogen to the unsaturated hydrocarbon to form saturated hydrocarbon.

Complete answer:
Alkenes are those carbon chains in which a double bond is present. The general formula is ${{C}_{n}}{{H}_{2n}}$.
Hexane is a compound of the alkane group and it is the sixth compound because of its six carbon atoms chain. The formula of hexane is ${{C}_{6}}{{H}_{14}}$. The open-chain structure of hexane will be:
$C{{H}_{3}}-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{3}}$
Hydrogenation is a process in which there is the addition of hydrogen to the unsaturated hydrocarbon to form saturated hydrocarbon. So, there are three alkenes, i.e., hexene, hex-2-ene, and hex-3-ene.
Hexene is an alkene in which a double bond is present between the first and the second carbon atoms. When it is hydrogenated then we get hexane. The reaction is given below:
$C{{H}_{3}}-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{2}}-CH=C{{H}_{2}}+{{H}_{2}}\to C{{H}_{3}}-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{3}}$
Hex-2-ene is an alkene in which the double bond is present between the second and the third carbon atoms. When it is hydrogenated then we get hexane. The reaction is given below:
$C{{H}_{3}}-C{{H}_{2}}-C{{H}_{2}}-CH=CH-C{{H}_{3}}+{{H}_{2}}\to C{{H}_{3}}-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{3}}$
Hex-3-ene is an alkene in which the double bond is present between the third and the fourth carbon atoms. When it is hydrogenated then we get hexane. The reaction is given below:
$C{{H}_{3}}-C{{H}_{2}}-CH=CH-C{{H}_{2}}-C{{H}_{3}}+{{H}_{2}}\to C{{H}_{3}}-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{3}}$

Note:
There is another alkene that can be converted into hexane, but the alkene has two double bonds, i.e., hex-1, 3-diene, and when it is hydrogenated with two moles of hydrogen, we get hexane. The reaction is given below:
$C{{H}_{3}}-C{{H}_{2}}-CH=CH-CH=C{{H}_{2}}+{{H}_{2}}\to C{{H}_{3}}-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{3}}$