DIRECTIONS: These are Assertion-Reason type questions. Question contains two statements:Statement-1 (Assertion) and Statement-2 (Reason). Answer these questions from the following four options.
Statement-1 :Electrical conductivity of semiconductors increases with increasing temperature.
Statement-2 :With increase in temperature, large number of electrons from the valence band can jump to the conduction band.
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Solution
In case of semiconductors, the gap between valence band and the conduction band is small and therefore some of the electrons may jump from valence band to conduction band and thus on increasing temperature conductivity is also increased.
DIRECTIONS: These are Assertion-Reason type questions. Question contains two statements:Statement-1 (Assertion) and Statement-2 (Reason). Answer these questions from the following four options.
Statement-1 :In close packing of spheres, a tetrahedral void is surrounded by four spheres whereas an octahedral void is surrounded by six spheres.
Statement-2 :A tetrahedral void has a tetrahedral shape whereas an octahedral void has an octahedral shape
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Solution
Tetrahedral void is so called because it is surrounded by four spheres tetrahedrally while octahedral void isso called because it is surrounded by six spheres octahedrally.
DIRECTIONS: These are Assertion-Reason type questions. Question contains two statements:Statement-1 (Assertion) and Statement-2 (Reason). Answer these questions from the following four options.
Statement-1 :Crystalline solids have long range order.
Statement-2 :Amorphous solids have short range order
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Solution
In crystalline solids constituents are arranged in definite orderly arrangement. This regular arrangement of constituents extends throughout the three dimensional network of crystal. Thus crystalline substances said to have long range order. Whereas amorphous solids have no regular arrangement.
DIRECTIONS: These are Assertion-Reason type questions. Question contains two statements:Statement-1 (Assertion) and Statement-2 (Reason). Answer these questions from the following four options.
Statement-1 :Space or crystal lattice differ in symmetry of the arrangement of points.
Statement-2 : nλ = 2dsinθ , is known as Bragg’s equation.
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Solution
Space or crystal lattice is a regular repeating arrangement of points in space and forms the basis of classification of all structures.
DIRECTIONS: These are Assertion-Reason type questions. Question contains two statements:Statement-1 (Assertion) and Statement-2 (Reason). Answer these questions from the following four options.
Statement-1:In any ionic solid (MX) with Schottky defects,the number of positive and negative ions are same.
Statement-2 :Equal number of cation and anion vacancies are present
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Solution
Schottky defect is due to missing of equal number of cations and anions.
DIRECTIONS: These are Assertion-Reason type questions. Question contains two statements:Statement-1 (Assertion) and Statement-2 (Reason). Answer these questions from the following four options.
Statement-1 :In crystal lattice, the size of the tetrahedral hole is larger than an octahedral hole.
Statement-2 :The cations occupy less space than anions in crystal packing.
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Solution
Tetrahedral holes are smaller in size than octahedral holes. Cations usually occupy less space than anions.