1
MCQ (Single Correct Answer)

AIPMT 2012 Mains

Structure of a mixed oxide is cubic close packed (ccp). The cubic unit cell of mixed oxide is composed of oxide ions. One fourth of the tetrahedral voids are occupied by divalent metal A and the octahedral voids are cooupied by a monovalent metal B. The formula of the oxide is
A
ABO2
B
A2BO2
C
A2B3O4
D
AB2O2

Explanation

Number of atoms in cubic close packing = 4 = O2-

Number of tetrahedral voids = 2 × N = 2 × 4

Number of A2+ ions = 8 $$ \times $$ $${1 \over 4}$$ = 2

Number of octahedral voids = Number of B+ ions = N = 4

Ratio of ions will be,

O2– : A2+ : B+ = 4 : 2 : 4 = 2 : 1 : 2

Formula of oxide = AB2O2
2
MCQ (Single Correct Answer)

AIPMT 2012 Prelims

A metal crystallises with a face-centred cubic lattice. The edge of the unit cell is 408 pm. The diameter of the metal atom is
A
288 pm
B
408 pm
C
144 pm
D
204 pm

Explanation

Given $$a$$ = 408 pm

For the face centred cubic structure

r = $${a \over {2\sqrt 2 }}$$ = $${{408} \over {2\sqrt 2 }}$$ = 144 pm

$$ \therefore $$ Diameter = 2r = 2$$ \times $$144 = 288 pm
3
MCQ (Single Correct Answer)

AIPMT 2011 Mains

A solid compound XY has NaCl structure. If the radius of the cation is 100 pm, the radius of the anion (Y$$-$$) will be
A
275.1 pm
B
322.5 pm
C
241.5 pm
D
165.7 pm

Explanation

For NaCl crystal, $${{{r_ + }} \over {{r_ - }}} = 0.414$$

Given, r+ = 100 pm

$$ \therefore $$ $${{100} \over {{r_ - }}} = 0.414$$

$$ \Rightarrow $$ $${r_ - } = {{100} \over {0.414}}$$ = 241.5 pm
4
MCQ (Single Correct Answer)

AIPMT 2010 Prelims

AB crystallizes in a body centered cubic lattice with edge length '$$a$$' equal to 387 pm. The distance between two oppositely charged ions in the lattice is
A
335 pm
B
250 pm
C
200 pm
D
300 pm

Explanation

For a bcc lattice, 2(r+ + r) = $$\sqrt 3 a$$

$$ \therefore $$ r+ + r = $${{\sqrt 3 \times 387} \over 2}$$ = 335 pm

EXAM MAP

Joint Entrance Examination

JEE Advanced JEE Main

Medical

NEET

Graduate Aptitude Test in Engineering

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