Engineering Chemistry MCQ (Chirality)

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Engineering Chemistry MCQ (Chirality)

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1. Chiral molecules are those which are?
a) Shows geometrical isomerism
b) Superimposable on their mirror images
c) Not superimposable on their mirror images
d) Unstable molecules
Answer: c
Explanation: Chiral molecules are those which are not superimposable on their mirror images. The presence of an asymmetric carbon atom is one of several structural features that induce chirality in organic and inorganic molecules.

2. Which of the following is not an example of chiral object?
a) Cylindrical helix
b) Square box
c) Sandal or shoe
d) Glove
Answer: b
Explanation: A square box is not chiral as it gives super-imposable mirror image. All the other mentioned options does not give the super-imposable mirror images.

3. For any given substance, the amount of rotation does not depends upon _________
a) Wavelength of light used
b) Nature of the solvent
c) Temperature
d) Pressure
Answer: d
Explanation: For any given substance, the amount of rotation depends upon the concentration, nature of solvent, temperature, length of layer traversed and the wavelength of light used. It does not depend upon the pressure conditions.

4. If the rotation of the plane is clockwise, the substance is dextrorotatary.
a) True
b) False
Answer: a
Explanation: If the rotation of the plane is clockwise, the substance is dextro
rotatary. And if the rotation of the plane is anti-clockwise, the substance is leavorotatary.

5. The specific rotation is inversely proportional to _________
a) Observed rotation
b) Temperature
c) Concentration of solution
d) D-line of sodium vapour light
Answer: c
Explanation: The specific rotation is inversely proportional to the concentration of solution and length of sample tube.

6. 0.5 g of an optically active compound was dissolved in 2mL of solvent at 250C. The solution was kept in a cell of length 10 cm and observed rotation was +100 . What is the specific rotation of its enantiomer?
a) -400
b) +400
c) -100
d) +100
Answer: b
Explanation: [α] = α/lC = +100/(1*0.5/2) = +400.

7. To avoid excessive high value of molecular rotation, concentration is taken as _________
a) 1 centi-mole/mL
b) 1 milli-mole/mL
c) 1 mole/mL
d) 1 kilo-mole/mL
Answer: a
Explanation: To avoid excessive high value of molecular rotation, concentration is taken as 1 centi-mole/mL.

8. Chiral molecules which are non-super-imposable mirror images of each other are called _________
a) Diastereomers
b) Meso compounds
c) Racemic mixture
d) Enantiomers
Answer: d
Explanation: Chiral molecules which are non-superimposable mirror images of each
other are called enantiomers. Enantiomer members often have different chemical
reactions with other enantiomer substances.

9. Select the correct statement from the following option.
a) Enantiomer rotate plane of polarised light in opposite direction and to different extent
b) Enantiomer rotate plane of polarised light in same direction but to different extent
c) Enantiomer rotate plane of polarised light in same direction and to same extent
d) Enantiomer rotate plane of polarised light in opposite direction but to same extent
Answer: d
Explanation: Enantiomer rotate plane of polarised light in opposite direction but to same extent. Enantiomer members often have different chemical reactions with other enantiomer substances.

10. Enantiomerism is the phenomenon of existence of enantiomers in a single structural formula, in _________ configuration.
a) Same
b) Opposite
c) Same as well as opposite
d) Initially opposite and then same
Answer: b
Explanation: Enantiomerism is the phenomenon of existence of enantiomers in a single structural formula but in opposite configuration.

11. Select the incorrect statement from the following option.
a) The physical properties of enatiomers are identical
b) In symmetrical environment, the chemical properties of enantiomers are identical
c) The enantiomers react at same rate and form products in same amounts in assymetrical environment
d) Enantiomers have different solubilities in the same chiral solvent
Answer: c
Explanation: The enantiomers react at different rate and form products in different amounts in assymetrical environment. All the other options are correct.

12. Optical activity can also result from the lack of molecular symmetry in molecules.
a) True
b) False
Answer: a
Explanation: Optical activity can also result from the lack of molecular symmetry in molecules which do not have chiral carbon.

13. The plane which divides the molecule into two equal parts so that each half is the mirror image of other half is called _________
a) Centre of symmetry
b) Plane of symmetry
c) Axis of symmetry
d) Angle of symmetry
Answer: b
Explanation: The plane divides the molecule into two equal parts so that each half is
the mirror image of other half is called plane of symmetry. Centre of symmetry is
the central point about which the molecule is symmetrical.

14. When a molecule has a plane of symmetry, it will be ______________
a) Optically inactive
b) Optically active
c) Both optically active & inactive
d) Enantiomer
Answer: a
Explanation: When a molecule has a plane of symmetry, it will be optically inactive, even though it might contain chiral carbon.

15. A centre of symmetry is equivalent to _________ fold alternating axis of symmetry.
a) One
b) Two
c) Three
d) Four
Answer: b
Explanation: A centre of symmetry is equivalent to two-fold alternating axis of symmetry.

16. Diastereomers are _________
a) Geometrical isomers
b) Mirror images
c) Non-mirror images
d) Unstable molecules
Answer: c
Explanation: Diastereomers are not mirror images of each other. Diastereomerism
occurs when two or more stereo isomers of a compound have different
configurations at one or more of the equivalent stereo centers and are not mirror images of each other.

17. A plane of symmetry is equivalent to _________ fold alternating axis of symmetry.
a) One
b) Two
c) Three
d) Four
Answer: a
Explanation: A centre of symmetry is equivalent to one-fold alternating axis of symmetry.

18. As the optical activity changes with the wavelength of light, it is necessary not to use monochromatic light to measure optical activity.
a) True
b) False
Answer: b
Explanation: As the optical activity changes with the wavelength of light, it is
necessary to use monochromatic light to measure optical activity.