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Ecdysone is an insect hormone that controls molting. In a polarimetric experiment, 70.00 mg of ecdysone was dissolved in 10.00 mL of chloroform, and the solution was placed in a 2.0 cm path-length cell. The optical rotation was measured at 20 °C using the yellow sodium D line near 589 nm wavelength. If the rotation observed was of +0.087°, calculate the 20Davalue for ecdysone.

Answer :

dsdrajlin

Answer:

The specific rotation is 62 °.mL . dm⁻¹ g⁻¹.

Explanation:

In a polarimetric experiment, we can calculate the specific rotation ([tex][\alpha ]_{D}^{20}[/tex]) for ecdysone using the following expression:

[tex][\alpha ]_{D}^{20} =\frac{\alpha }{l \times c }[/tex]

where,

α is the angle of rotation

l is the path length in decimeters (2.0 cm = 0.20 dm)

c is the concentration in g/mL

Concentration is:

[tex]c=\frac{massof solute}{volumeof solution} =\frac{70.00 \times 10^{-3}g  }{10.00mL} =7.000 \times 10^{-3}g/L[/tex]

Then,

[tex][\alpha ]_{D}^{20} =\frac{\alpha }{l \times c }=\frac{0.087\textdegree }{0.20dm \times 7.000 \times 10^{-3}g/mL } =62 \textdegree .mL .dm^{-1}. g^{-1}[/tex]

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