(i) Ethane will undergo Substitution reactions.
Reason — In case of ethane, all of its 4 valencies are satisfied by hydrogen atoms forming single bond and so they are less reactive and undergo substitution reaction only.
(ii) Ethene will undergo Addition reactions.
Reason — In case of ethene, the valencies of atleast 2 carbon atoms are not fully satisfied by hydrogen atoms. The availability of electrons in the double bond makes them more reactive and hence they undergo addition reactions only.