A compound formed by elements $$X$$ and $$Y$$ crystallises in a cubic structure in which the $$X$$ - atoms are at the corners of a cube and the $$Y$$ - atoms are at the face centres. The formula of the compound is
A.
$$X{Y_3}$$
B.
$${X_3}Y$$
C.
$$XY$$
D.
$$X{Y_2}$$
Answer :
$$X{Y_3}$$
Solution :
In unit cell, $$X$$ - atoms at the comers $$ = \frac{1}{8} \times 8 = 1$$
$$Y$$ - atoms at the face centres $$ = \frac{1}{2} \times 6 = 3$$
Ratio of $$X$$ and $$Y$$ = 1 : 3.
Hence, formula is $$X{Y_3}.$$
Releted MCQ Question on Physical Chemistry >> States of Matter Solid, Liquid and Gas
Releted Question 1
Equal weights of methane and oxygen are mixed in an empty container at $${25^ \circ }C.$$ The fraction of the total pressure exerted by oxygen is