A 0.140 M solution of an enantiomerically pure chiral co 1-dm sample container.

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 +0.18* in a (a) What is the specific rotation of D? 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? Number deg mL g dm | 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 mL g. dm deg (f) What is the observed rotation of 100 mL of a solution that contains 0.01 mole of D and 0.005 mole of L? (Assume a 1-dm path length.) e) What is the specific rotation of L, the enantiomer of after the dilution described in part (c)? Number deg ml g dm deg Next Ex ? Hint

Explanation / Answer

a)

concentration = 0.140 x 128 = 17.92 g / L = 0.01792 g/mL

observed rotation = + 0.18 o

specific rotation = observed rotation / l x concnetration

                             = 0.18 / 1 x 0.01792

specific rotation = 10.04 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 = 0.01792 / 2 = 0.00896

observed rotation = 10.04 x0.00896 x 1

observed rotation = 0.090 deg

d)

specific rotation is uneffected by dilution

specific rotation = 10.04

e)

specific rotation of L = - 10.04

f)

moles= 0.01 - 0.005 = 0.005

concentration = 0.005 / 0.1 = 0.05 M

                       = 0.05 x 128/ 1000

                       = 0.0064

observed rotation = 0.0064 x 10.04 x 1

observed rotation = 0.064

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