Can you please explain why numbers 19,20,21,22,23,25 are wrong and why the answer written next to it is correct.

3 19. D The reaction of cyclohexene and Cl2 yields A. 1-chlorocyclohexene. B. 1,2-dichlorocyclohexane. C. 1,3-dichlorocyclohexane. (B) 2,3-dichlorocyclohexane. E. 3,4-dichlorocyclohexane. 20. The hydrogenation of an alkene gives a(n) A 21. B what is the IUPAC name of the following compound? A. 5-methyl-2-hexyne B. 2-methyl-4-hexyne D. 2,4-dimethyl-4-pentyne E. 1,1-dimethyl-3-pentyne C. 4-isopropyl-2-pentyne E 22. A saran, used as a plastic wrap for foods, is a polymer with the following structure. What is the monomer unit of Saran? (A.1,1-dichloroethaneB.1-chloroethaneC.1-chloroethyneD.ethaneE.1,1-dichloroethene B 23. What intermolecular force generally accounts for the higher boiling points of alcohols compared to alkenes? A. ionic B. hydrogen bonding (2) dispersion D. London E. ion-dipole 24. 13 -butanol (CH3CHOHCH2CH3) is classified as a(n) A. primary alcohol B. secondary alcohol C. tertiary alcohol D. ether 25. What is the correct IUPAC name for the compound shown here? A. 2,2-dimethyl-6-hexanol B. 2,3-dimethyl-7-heptanol D. 3,3-dimethyl-6-hexanol E. 5-isopropyl-1-hexanol C. 5,6-dimethyl-1-heptanol