Which of the following statements is not true about the hexagonal close packing?
(A) The coordination number is 12.
(B) It has 74% packing efficiency.
(C) Tetrahedral voids of the second layer are covered by the spheres of the third layer.
(D) In this arrangement spheres of the fourth layer are exactly aligned with those of the first layer.
(A) The coordination number is 12.
(B) It has 74% packing efficiency.
(C) Tetrahedral voids of the second layer are covered by the spheres of the third layer.
(D) In this arrangement spheres of the fourth layer are exactly aligned with those of the first layer.
(D) In this arrangement spheres of the fourth layer are exactly aligned with those of the first layer.
Which of the following statements is not true about amorphous solids?
(A) On heating they may become crystalline at certain temperature.
(B) They may become crystalline on keeping for long time.
(C) Amorphous solids can be moulded by heating.
(D) They are anisotropic in nature.
Which of the following is true about the value of refractive index of quartz glass?
(A) Same in all directions
(B) Different in different directions
(C) Cannot be measured
(D) Always zero
Which of the following conditions favours the existence of a substance in the solid state?
(A) High temperature
(B) Low temperature
(C) High thermal energy
(D) Weak cohesive forces
Which of the following Defects is also known as dislocation defect?
(A) Frenkel defect
(B) Schottky defect
(C) Non-stoichiometric defect
(D) Simple interstitial defect
Which of the following is not true about the ionic solids?
(A) Bigger ions form the close packed structure.
(B) Smaller ions occupy either the tetrahedral or the octahedral voids depending upon their size.
(C) Occupation of all the voids is not necessary.
(D) The fraction of octahedral or tetrahedral voids occupied depends upon the radii of the ions occupying the voids.
Which stoichiometric defect does not change the density of the crystal?
(A) Frenkel defect
(B) Schottky defect
(C) Interstitial defect
(D) F-centres
Solid A is very hard electrical insulator in solid as well as in molten state and melts at an extremely high temperature. What type of solid is it?
(A) Ionic solid
(B) Molecular solid
(C) Covalent solid
(D) Metallic solid
Which of the following alcohols will give the most stable carbocation during dehydration?
(a) 2-methyl-1-propanol.
(b) 2-methyl-2-propanol.
(c) 1-Butanol.
(d) 2-Butanol.
How is electrical conductance of a conductor related with length and area of cross-section of the conductor?
a. G = l.a.k−1
b. G = k.l.a−1
c. G = k.a.l−1
d. G = k.l.a−2
The order of reactivity of the following alcohols with halogen acids is
Which of the following will have the maximum dipolemoment?
(a) CH3F.
(b) CH3Cl.
(c) CH3Br.
(d) CH3I.
Assertion: The two strands of DNA are complementary to each other.
Reason: The hydrogen bonds are formed between specific pairs of bases.
A. Assertion and reason both are correct statements and reason is correct explanation for assertion.
B. Assertion and reason both are correct statements but reason is not correct explanation for assertion.
C. Assertion is correct statement but reason is wrong statement.
D. Assertion is wrong statement but reason is correct statement.
The letter ‘D’ in carbohydrates signifies-
(a) dextrorotatory
(b) configuration
(c) diamagnetic nature
(d) mode of synthesis
Which of the following compounds will be most easily attacked by an electrophile?