1
MCQ (Single Correct Answer)

AIPMT 2007

If NaCl is doped with 10$$-$$4 mol% of SrCl2, the concentration of cation vacancies will be (NA = 6.02 $$ \times $$ 1023 mol$$-$$1)
A
6.02 $$ \times $$ 1016 mol$$-$$1
B
6.02 $$ \times $$ 1017 mol$$-$$1
C
6.02 $$ \times $$ 1014 mol$$-$$1
D
6.02 $$ \times $$ 1015 mol$$-$$1

Explanation

As each Sr2+ ion introduces one cation vacancy, therefore concentration of cation vacancies = mole % of SrCl2 added.

$$ \therefore $$ Concentration of cation vacancies

= 10–4 mole %

= $${{{{10}^{ - 4}}} \over {100}} \times 6.023 \times {10^{23}}$$

= $$6.023 \times {10^{23}}$$ $$ \times $$ 10-6

= $$6.023 \times {10^{17}}$$
2
MCQ (Single Correct Answer)

AIPMT 2007

The fraction of total volume occupied by the atoms present in a simple cube is
A
$${\pi \over {3\sqrt 2 }}$$
B
$${\pi \over {4\sqrt 2 }}$$
C
$${\pi \over 4}$$
D
$${\pi \over 6}$$

Explanation

The maximum properties of the available volume which may be filled by hard sphere in simple cubic arrangement is $${\pi \over 6}$$ or 0.52.
3
MCQ (Single Correct Answer)

AIPMT 2006

CsBr crystallises in a body centered cubic lattice. The unit cell length is 436.6 pm. Given that the atomic mass of Cs = 133 and that of Br = 80 amu and Avogadro number being 6.02 $$ \times $$ 1023 mol$$-$$1, the density of CsBr is
A
4.25 g/cm3
B
42.5 g/cm3
C
0.425 g/cm3
D
8.25 g/cm3

Explanation

Density of CsBr = $${{Z \times M} \over {V \times {N_A}}}$$

= $${{1 \times 213} \over {{{\left( {436.6 \times {{10}^{ - 10}}} \right)}^3} \times 6.023 \times {{10}^{23}}}}$$

= 4.25 g/cm3
4
MCQ (Single Correct Answer)

AIPMT 2006

The appearance of colour in solid alkali metal halides is generally due to
A
interstitial positions
B
F.-centres
C
Schottky defect
D
Frenkel defect

Explanation

F-centres are the sites where anions are missing and instead electrons are present. They are responsible for colours.

EXAM MAP

Joint Entrance Examination

JEE Advanced JEE Main

Medical

NEET

Graduate Aptitude Test in Engineering

GATE CSE GATE ECE GATE ME GATE PI GATE EE GATE CE GATE IN