Question:

A compound $M_pX_q$ has cubic close packing $(ccp)$ arrangement of $X$. Its unit cell structure shown below. The empirical formula of the compound is

Updated On: Jul 5, 2022
  • $MX$
  • $MX_2$
  • $M_2X$
  • $M_5X_{14}$
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The Correct Option is B

Solution and Explanation

$8\,X$ atoms present at the corners. Atoms contribute to $1$ unit cell $=\frac{1}{8}\times8=1$ $6 \,X$ atoms present at the face centres. Atoms contribute to $1$ unit cell $=6\times\frac{1}{2}=3$ Total $X$ atoms $= 3 + 1=4$ $4\,M$ atoms present at edge centres. Atoms present in $1$ unit cell $=4\times\frac{1}{4}=1$ $1\,M$ atom present at body centre and it contribute completely to $1$ unit cell. Thus, total $M$ atoms in one unit cell $=1 + 1 = 2$ Ratio is $M : X :\,: 2 : 4 :\,: 1 : 2$ Thus, empirical formula is $MX_2$.
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Concepts Used:

Solid State

Solids are substances that are featured by a definite shape, volume, and high density. In the solid-state, the composed particles are arranged in several manners. Solid-state, in simple terms, means "no moving parts." Thus solid-state electronic devices are the ones inclusive of solid components that don’t change their position. Solid is a state of matter where the composed particles are arranged close to each other. The composed particles can be either atoms, molecules, or ions. 

Solid State

Types of Solids:

Based on the nature of the order that is present in the arrangement of their constituent particles solids can be divided into two types;

  • Amorphous solids behave the same as super cool liquids due to the arrangement of constituent particles in short-range order. They are isotropic and have a broad melting point (range is about greater than 5°C).
  • Crystalline solids have a fixed shape and the constituent particles are arranged in a long-range order.