A 0.140 M solution of an enantiomerically pure chiral co 1-dm sample container.
ID: 1032492 • Letter: A
Question
A 0.140 M solution of an enantiomerically pure chiral co 1-dm sample container. The molar mass of the co D has an observed rotation of +0.26° in is 179.0 g/mol. b) What is the observed rotation if this solution s mixed with an equal volume of a solution that is 0.140 M in L, the enantiomer of D? (a) What is the specific rotation of D? Number deg mL. g dm Number deg (c) What is the observed rotation if the solution of D is diluted with an equal volume of solvent? (d) What is the specific rotation of D after the dilution described in part (c)? Number Number deg mi g dm deg e) What is the specific rotation of L, the enantiomer of , after the dilution described in part (c)? () What is the observed rotation of 100 mL of a mole of L? (Assume a 1-dm path length.) Number deg ml g dm degExplanation / Answer
a)
concentration = 0.140 x 179 = 25.06 g / L = 0.02506 g/mL
observed rotation = + 0.26o
specific rotation = observed rotation / l x concnetration
= 0.26 / 1 x 0.02506
specific rotation = 10.4 deg .mL / g.dm
b)
equial volume and equal concnetrations of solutions mixed , racemic mixure formed.
observed rotation = 0 deg
c)
volume doubled , then concentration is halved.
c = 0.02506 / 2 = 0.01253
observed rotation = 10.4 x 0.01253 x 1
observed rotation = 0.130 deg
d)
specific rotation is uneffected by dilution
specific rotation = 10.4
e)
specific rotation of L = - 10.4
f)
moles= 0.01 - 0.005 = 0.005
concentration = 0.005 / 0.1 = 0.05 M
= 0.05 x 179 / 1000
= 0.00895
observed rotation = 0.00895 x 10.4 x 1
observed rotation = 0.093
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