I got this question wrong, googled it, and didn't find any answers to how this is the right answer: 12) Chemistry – Multiple Choice A student is interested in the optical properties of chiral [KYE-ruhl]
molecules, so she successively performs a chlorination, bromination [broh-min-AY-shun], and an
iodination [eye-oh-dah-NAY-shun] of methane. However, she is disappointed to find out that the resulting
product demonstrates no optical rotation of polarized light. Which of the following best explains this?
W) She prepared a racemic [ray-SEEM-ik] mixture
X) Only certain chiral [KYE-ruhl] molecules demonstrate optical rotation
Y) Geometric isomers demonstrate optical rotation, not stereoisomers [stereo-EYE-soh-murs]
Z) Only larger, more complex chiral molecules demonstrate optical rotation
ANSWER: W) SHE PREPARED A RACEMIC MIXTURE

On successive chlorination, bromination and iodination, the molecule (hydrocarbons) they undergo in making both the enantiomers in equal amount. If both enantiomers are formed in equal amounts then it will be a racemic mixture which rotates plane polarized light in equal amount in both directions. The net rotation of racemic mixture is zero so it will be optically inactive.

Ok, thank you!