Is lactic acid optically inactive.

Lactic acid is actually optically active, meaning it can rotate the plane of polarized light. It exists in two stereoisomeric forms: L-lactic acid and D-lactic acid. These isomers are mirror images of each other and are referred to as enantiomers. The property of being optically active arises from the asymmetry in the arrangement of atoms around the chiral carbon atom in these enantiomers.

L-lactic acid is the naturally occurring form found in various biological processes, such as during the fermentation of sugars by bacteria and in the metabolism of humans and animals. D-lactic acid can also be produced by certain bacterial species. The mixture of equal amounts of L-lactic acid and D-lactic acid is called racemic lactic acid and is optically inactive due to the cancellation of the optical rotations of the two enantiomers.

So, while individual L-lactic acid and D-lactic acid molecules are optically active, a racemic mixture of the two isomers would be optically inactive.