Organic Chemistry Questions and Answers – Polarimeter | Organic Chemistry Multiple Choice Questions and Answers

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Questions
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°

Answer:+9.6°
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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

Answer:α gets double
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°

Answer:+25°
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

Answer:CH2Cl
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)

Answer:25%(R) 75%(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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