(a) Eight isomeric alcohols are possible:





b)  Primary alcohol: pentan-1-ol; methylbutan-1-ol; 3-methyl-1-ol; 2,2Dimethylpropan-1-ol.

Secondary alcohol: Pentan-2-ol; 3-methylbutan-2-ol; pentan-3-ol

Tertiary alcohol: 2-methylbutan-2-ol

The mechanism  of the reaction involves the following three step:

Step 1: Proptonation of ethene to form carbocation by electrophilic attack of H₃O⁺.



Step 2: Nucleophilic attack of water on carbocation.



Step 3: Deprotonation to form an ethanol.

(HCl—ZnCl₂) is lucas reagent, lucas reagent react with alcohol however it does not react with primary alcohol but readily gives turbidity with tertiary alcohols.

a) Reaction with (HCl—ZnCl₂):

Butan-1-ol is primary alcohol thus no reaction occur.
where as 2-methyl butan-2-ol is tertiary alcohol, it forms 2-chloro-2-methylbutane.

 
b) Reaction with HBr:

c) Reaction with SOCl₂: