Sucrose ( $C X_{12} H X_{22} O X_{11}$ , molar mass $342 g mo l^{- 1}$ ) has eight free hydroxyl groups. Assume all of them are acetylated by excess acetic anhydride and each -OH group consumes one molecule of $(CH X_{3} CO) X_{2} O$ . How many moles of acetic anhydride are consumed by $171 g$ of sucrose? (Give the answer as a number of moles, nearest integer.)

Numerical answer type, tolerance 0.5.

Answer: 4

Moles of sucrose = 171/342 = 0.5 mol. Each mole has 8 -OH groups, giving sucrose octaacetate, and each -OH uses one mole of acetic anhydride. Moles of acetic anhydride = 0.5 x 8 = 4.

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