Reaction involved

Acid-catalyzed hydration of an alkene means addition of water in presence of acid: $\text{Alkene} + H_2O \xrightarrow{H^+} \text{Alcohol}$

This reaction proceeds through a carbocation intermediate and follows Markovnikov addition.

General outcome of hydration

In Markovnikov addition, the proton adds in such a way that the more stable carbocation is formed. Then water attacks that carbocation.

Since carbocation stability is: $3^\circ > 2^\circ > 1^\circ$ the reaction tends to form secondary or tertiary carbocations, and therefore gives secondary or tertiary alcohols.

Why ethene is excluded

Ethene on hydration gives ethanol: $CH_2=CH_2 \xrightarrow{H^+,H_2O} CH_3CH_2OH$ which is a primary alcohol.

But the question says except ethene, so this case is removed.

Check the options

• A: primary alcohol
  False, because except for ethene, acid-catalyzed hydration does not normally give primary alcohols.

• B: secondary or tertiary alcohol
  True. For alkenes other than ethene, Markovnikov hydration gives alcohols where the OH-bearing carbon is usually secondary or tertiary.

• C: mixture of primary and secondary alcohols
  False. Primary alcohol formation is not the normal outcome here.

• D: mixture of secondary and tertiary alcohols
  False as a general statement. A given alkene does not generally give a mixture of secondary and tertiary alcohols in acid-catalyzed hydration; rather, it gives a product that is either secondary or tertiary depending on the alkene.

Conclusion

Therefore, acid-catalyzed hydration of alkenes except ethene leads to formation of: $\boxed{\text{secondary or tertiary alcohol}}$ So the correct option is B.