A compound A B has rock salt type structure. The formula...

A compound $A B$ has rock salt type structure. The formula weight of $A B$ is $6.023 Y$ amu, and the closest $A-B$ distance is $Y^{1 / 3} \mathrm{~nm}$, where $Y$ is an arbitrary number. (a) Find the density of lattice (b) If the density of lattice is found to be $20 \mathrm{~kg} \mathrm{~m}^{-3}$, then predict the type of defect.

A compound $A B$ has rock salt type structure. The formula weight of $A B$ is $6.023 Y$ amu, and the closest $A-B$ distance is $Y^{1 / 3} \mathrm{~nm}$, where $Y$ is an arbitrary number.
(a) Find the density of lattice
(b) If the density of lattice is found to be $20 \mathrm{~kg} \mathrm{~m}^{-3}$, then predict the type of defect.

Key Concepts

Lattice Defects in Ionic Crystals

Defects, such as point defects, can significantly affect the physical properties of ionic crystals. In ionic solids, common defects include Schottky defects, where there is a vacancy of equal numbers of cations and anions, and Frenkel defects, where an ion is displaced from its normal lattice site to an interstitial site. Understanding which type of defect is present involves analyzing deviations in measured properties (like density) from the ideal crystalline state.

Lattice Parameter Determination

The lattice parameter is a measure of the repeated distance in a crystalline lattice and can be deduced from the shortest distance between ions or atoms in the structure. In many crystalline solids, especially in ionic compounds, information about the nearest neighbor distances is used to calculate the unit cell edge length, which in turn is essential to computing the unit cell volume and other properties like density.

Rock Salt Structure

This is a common ionic crystal structure where two types of ions (usually a cation and an anion) are arranged in a face?centered cubic lattice. In this structure, each ion is coordinated by six oppositely charged ions, forming an octahedral geometry. The understanding of this structure is fundamental to analyzing properties such as density, ionic radii relations, and pathways for defects.

Crystal Density Calculation

Crystal density is determined by dividing the mass contained in a unit cell by the volume of the unit cell. This calculation involves knowing the formula weight of the constituent formula unit, the number of formula units per unit cell, and how the lattice parameter (derived from interatomic distances) is related to the dimensions of the cell. It is a key concept in solid?state chemistry and materials science as it connects microscopic structure with macroscopic properties.

Transcript

Please give Ace some feedback