Final answer:
A monosaccharide ketopentose can have 8 possible stereoisomers, calculated using the formula 2^n, where n is the number of chiral centers, which is typically three for a ketopentose.
Step-by-step explanation:
The student asked how many stereoisomers are possible for a monosaccharide ketopentose. Ketopentoses are a type of monosaccharide that contain a ketone group and have five carbons in the backbone. The formula 2n, where n is the number of chiral centers, can be used to calculate the maximum number of stereoisomers for such compounds. A ketopentose typically has three chiral centers - corresponding to the three carbons that are not part of the ketone. Therefore, using the formula, the number of stereoisomers of a ketopentose can be calculated as 23 or 8 possible stereoisomers. Additionally, each of these stereoisomers can exist in two cyclic forms as anomers, alpha and beta, due to the cyclic structure formation in aqueous solutions. However, the original question only asks for the total number of stereoisomers, not accounting for the anomer forms.