Embibe Experts Solutions for Chapter: The Solid State, Exercise 1: ICSE-2018

Examine the defective crystal given below and answer the question that follows:

State if the above defect is stoichiometric or non-stoichiometric. How does this defect affect the density of the crystal? Also, write the term used for this type of defect.

An element occurs in body centred cubic structure. Its density is $8.0 \mathrm{g} {\mathrm{cm}}^{-3}$. If the cell edge is $250 \mathrm{pm}$, calculate the atomic mass of an atom of this element. (${\mathrm{N}}_{\mathrm{A}}=6.023\times {10}^{23} {\mathrm{mol}}^{-1}$).

The packing efficiency of simple cubic structure, body centred cubic structure and face centred cubic structure respectively is:

An element has atomic weight $93 \mathrm{g} {\mathrm{mol}}^{-1}$ and density $11.5 \mathrm{g} {\mathrm{cm}}^{-3}$. If the edge length of its unit cell is $300 \mathrm{pm}$, identify the type of unit cell. (${\mathrm{N}}_{\mathrm{A}}=6.023\times {10}^{23} {\mathrm{mol}}^{-1}$).

Calculate the radius of copper atom. The atomic weight of copper is $63.55 \mathrm{g} {\mathrm{mol}}^{-1}$. It crystallises in face centred cubic lattice and has density of $8.93 \mathrm{g} {\mathrm{cm}}^{-3}$ at $298 \mathrm{K}$. (${\mathrm{N}}_{\mathrm{A}}=6.023\times {10}^{23} {\mathrm{mol}}^{-1}$).

An alloy of gold ($\mathrm{Au}$) and cadmium ($\mathrm{Cd}$) crystallises with a cubic structure in which gold atoms occupy the corners and cadmium atoms fit into the face centres. What is the formula of this alloy?