How many optical isomers are possible for a compound having $3$ asymmetric carbon atoms?

The specific rotation of $(+)$-Mandelic acid is $+158^o$. What will be the specific rotation of a mixture containing $25\%$ $(-)$-Mandelic acid and $75\%$ $(+)$-Mandelic acid?

Which of the following compounds is optically active?

$(+)$ $2-$Methylbutan$-1-$ol and $(-)$ $2-$Methylbutan$-1-$ol have different values for which property?

Lactic acid,in which a methyl group,a hydroxyl group,a carboxylic acid group,and a hydrogen atom are attached to a central carbon atom,shows optical isomerism due to the molecular geometry at the:

The number of chiral carbons present in the molecule given below is......