Racemic mixture or not?
IUPAC advises against using the term racemic mixture because of its ambiguity.


  racemic mixture (obsolete) The term is confusing since it has been used as a synonym for both racemate and racemic conglomerate. Usage strongly discouraged.


The term that applies in this case is racemate.


  racemate An equimolar mixture of a pair of enantiomers. It does not exhibit optical activity.




There are three qualitatively different initial conditions to consider.

1. A racemate of (3S)-methylpentan-2-one and (3R)-methylpentan-2-one, nucleophile is not $\ce{OH-}$

Both enantiomers behave similarly, each yielding a stereocenter at the carboxylic carbon.



Verdict: not optically active but contains two pairs of equimolar enantiomers: $\mathrm{a), d)}$ and $\mathrm{b), c)}$. Even three if you count the reagents. Is a racemate if one relaxes the single pair criterium.

2. A racemate of (3S)-methylpentan-2-one and (3R)-methylpentan-2-one, nucleophile is $\ce{OH-}$

Verdict: not optically active, equimolarity is ensured, a pair of enantiomers. Is a racemate.

3. Either (3S)-methylpentan-2-one or (3R)-methylpentan-2-one, nucleophile is / is not $\ce{OH-}$

Verdict: optically active, does not contain enantiomers. Not a racemate.