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Free download in PDF Organic Chemistry Multiple Choice Questions and Answers for competitive exams. These short objective type questions with answers are very important for Board exams as well as competitive exams like UPSC, NDA, SSC etc. These short solved questions or quizzes are provided by Gkseries./p>
(1)
What does a polarimeter measure?
[A]
Polarity of the substance
[B]
Angle of rotation of an optical active compound
[C]
Concentration of the substance
[D]
pH of the substance
Answer: Angle of rotation of an optical active compound
(2)
A solution of 0.1 g/mL of a pure R enantiomer in a 1.0 dm (i.e., 10 cm) polarimeter rotates plane polarized light by +4.8°. What is the rotation observed on this solution in a 2 dm polarimeter?
[A]
+2.4°
[B]
+4.8°
[C]
+19°
[D]
+9.6°
(3)
Polarimeter works on the principle of which of the following?
[A]
polarisation of light
[B]
change of the electrical conductivity of solution with composition
[C]
change of angle of refraction with composition
[D]
change of electrical conductivity of solution with temperature
Answer: polarisation of light
(4)
What is the effect of the I on the specific optical rotation (α), if I gets double?
[A]
α gets double
[B]
α gets halved
[C]
α gets four times
[D]
α eight times
(5)
If a solution of a compound (30.0 g/100 mL of solution) has a measured rotation of +15° in a 2 dm tube, what is the specific rotation?
[A]
+50°
[B]
+25°
[C]
+15°
[D]
+7.5°
(6)
Which of the following groups has the highest priority according to the Cahn-Ingold-Prelog sequence rules?
[A]
CH3
[B]
CH2Cl
[C]
CH2OH
[D]
CHO
(7)
What is the percent composition of a mixture of (S)-(+)-2-butanol, α= +13.52°, and (R)-(-)-2-butanol, α = -13.52°, with a specific rotation α = +6.76°?
[A]
75%(R) 25%(S)
[B]
25%(R) 75%(S)
[C]
50%(R) 50%(S)
[D]
67%(R) 33%(S)
(8)
What can be said with certainty if a compound has α= -9.25°?
[A]
The compound has the (S) configuration
[B]
The compound has the (R) configuration
[C]
The compound is not a meso form
[D]
The compound possesses only one stereogenic center
Answer: The compound is not a meso form
(9)
Which of these is a comparatively insignificant factor affecting the magnitude of specific optical rotation?
[A]
Concentration of the substance of interest
[B]
Purity of the sample
[C]
Temperature of the measurement
[D]
Length of the sample tube
Answer: Temperature of the measurement
(10)
What is the specific optical rotation of (S)-malic acid at a concentration of 5.5 g/ mL in the solvent pyridine at 20°C at a wavelength of 589 nm?
[A]
the specific rotation is –27°
[B]
the specific rotation is +27°
[C]
the specific rotation is –17°
[D]
the specific rotation is +17°
Answer: the specific rotation is –27°
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