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# Calculate the specific rotations of the following samples ISBN: 9780321768414 33

## Solution for problem 32SP Chapter 5

Organic Chemistry | 8th Edition

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Problem 32SP

Calculate the specific rotations of the following samples taken at 25 °C using the sodium D line.

(a) 1.00 g of sample is dissolved in 20.0 mL of ethanol. Then 5.00 mL of this solution is placed in a 20.0-cm polarimeter tube. The observed rotation is 1.25° counterclockwise.

(b) 0.050 g of sample is dissolved in 2.0 mL of ethanol, and this solution is placed in a 2.0-cm polarimeter tube. The observed rotation is clockwise 0.043°.

Step-by-Step Solution:
Step 1 of 3

Here we have to calculate the specific rotations of the samples.

Given:

Step-1

(a)

Mass of sample = 1.00gm

Volume of ethanol = 20.0mL

Volume of sample = 5mL

Width of polarimeter tube  = 20.0cm= 2dm

Counter clockwise rotation = -1.25°

Specific rotation  can be calculated as follows:-

[α]lT = α/lc

Where:

[α]lT = specific rotation in degrees. (The correct units are deg cm2 g-1, but are usually just given as degrees).  l is the wavelength of light used for the observation (usually 589 nm, the D line of a sodium lamp unless otherwise specified.  This wavelength is responsible for the orange-yellow color of the common sodium vapor street light). T is the temperature in oC.

α = observed rotation in degrees.

l = cell path length in decimeters. (1 decimeter = 1 dm = 10 cm. A standard polarimeter tube is 1.00 dm in length.)

C = concentration in g ml-1 for a pure liquid compound (i.e., the liquid's density), or g 100 ml-1 for...

Step 2 of 3

Step 3 of 3

##### ISBN: 9780321768414

Organic Chemistry was written by and is associated to the ISBN: 9780321768414. The answer to “Calculate the specific rotations of the following samples taken at 25 °C using the sodium D line.(a) 1.00 g of sample is dissolved in 20.0 mL of ethanol. Then 5.00 mL of this solution is placed in a 20.0-cm polarimeter tube. The observed rotation is 1.25° counterclockwise.(b) 0.050 g of sample is dissolved in 2.0 mL of ethanol, and this solution is placed in a 2.0-cm polarimeter tube. The observed rotation is clockwise 0.043°.” is broken down into a number of easy to follow steps, and 74 words. The full step-by-step solution to problem: 32SP from chapter: 5 was answered by , our top Chemistry solution expert on 05/06/17, 06:41PM. This full solution covers the following key subjects: Rotation, tube, counterclockwise, Dissolved, ethanol. This expansive textbook survival guide covers 25 chapters, and 1336 solutions. This textbook survival guide was created for the textbook: Organic Chemistry, edition: 8. Since the solution to 32SP from 5 chapter was answered, more than 630 students have viewed the full step-by-step answer.

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Calculate the specific rotations of the following samples

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