Question
What is an impurity defect? What are its types? Explain the formation of vacancies through aliovalent impurity with example.
✓
Answer
Impurity defect : This defect arises when foreign atoms, that is, atoms different from the host atoms are present in the crystal lattice.There are two types of impurity defects namely
Examples : Solid solutions of metals (alloys). For example. Brass in which host atoms are of Cu which are replaced by impurity of Zn atoms. In this Zn atoms occupy regular sites while Cu atoms occupy substituted sites.
Brass
Vacancy through aliovalent impurity :
By addition of impurities of aliovalent ions :
Vacancy through aliovalent ion
When aliovalent ion like $Sr ^{2+}$ in small amount is added by additing $SrCl _2$ to NaCl during its crystallisation, each $Sr ^{2+}$ ion (oxidation state $2+$ ) removes $2 Na ^{+}$ions from their lattice points, to maintain electrical neutrality. Hence one of vacant lattice site is occupied by $Sr ^{2+}$ ion while other site remains vacant.
Interstitial impurity defect:
Stainless steel
A defect in solid in which the impurity atoms occupy interstitial vacant spaces of lattice structure is called interstitial impurity defect.
For example, in steel, normal lattice sites are occupied by Fe atoms but interstitial spaces are occupied by carbon atoms.
- Substitutional defects and
- Interstitial defects.
Examples : Solid solutions of metals (alloys). For example. Brass in which host atoms are of Cu which are replaced by impurity of Zn atoms. In this Zn atoms occupy regular sites while Cu atoms occupy substituted sites.
Brass
Vacancy through aliovalent impurity :
By addition of impurities of aliovalent ions :
Vacancy through aliovalent ion
When aliovalent ion like $Sr ^{2+}$ in small amount is added by additing $SrCl _2$ to NaCl during its crystallisation, each $Sr ^{2+}$ ion (oxidation state $2+$ ) removes $2 Na ^{+}$ions from their lattice points, to maintain electrical neutrality. Hence one of vacant lattice site is occupied by $Sr ^{2+}$ ion while other site remains vacant.
Interstitial impurity defect:
Stainless steel
A defect in solid in which the impurity atoms occupy interstitial vacant spaces of lattice structure is called interstitial impurity defect.
For example, in steel, normal lattice sites are occupied by Fe atoms but interstitial spaces are occupied by carbon atoms.
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
How are tetrahedral and octahedral voids formed?
Predict the type of cubic lattice of a solid element having edge length of 400 pm and density is 6.25 g/ml
(Atomic mass of element = 60)
Define: Nanoscience
Write chemical reaction for the preparation of polyacrylonitrile.
(Atomic mass of element = 60)
Define: Nanoscience
Write chemical reaction for the preparation of polyacrylonitrile.
What are anode and cathode of $H2-O2$ fuel cell ? Name the electrolyte used in it. Write electrode reactions and net cell reaction taking place in the fuel cell.
→From the following data for the decomposition of azoisopropane,
$\left( CH _2\right)_2 CHN = NCH \left( CH _3\right)_2 \rightarrow N _2+ C _6 H _{14}$ estimate the rate of the reaction when total pressure is 0.75 stm .
→$\left( CH _2\right)_2 CHN = NCH \left( CH _3\right)_2 \rightarrow N _2+ C _6 H _{14}$ estimate the rate of the reaction when total pressure is 0.75 stm .
| Time/s | Total pressure/atm |
| 0 | $0.65$ |
| 200 | $1.0$ |
Obtain a relation for the density of the unit cell and radius of atom or sphere for the following :
(1) Simple cubic (scc) crystal
(2) Body centred cubic (bcc) crystal
(3) Face centred cubic (fcc) crystal.
(1) Simple cubic (scc) crystal
(2) Body centred cubic (bcc) crystal
(3) Face centred cubic (fcc) crystal.
What are amines? How are they classified?
Predict whether the following
reactions would occur spontaneously
under standard state conditions.
a. $Ca_{(s)} + Cd^{2+}_{(aq)} \rightarrow Ca^{2+}_{(aq)} + Cd_{(s)}$
b. $2 Br-_{(s)} + Sn^{2+}(aq) \rightarrow Br_2_{(l)} + Sn_{(s)}$
c. $2Ag_{(s)} + Ni^{2+}_{(aq)} \rightarrow 2 Ag^+_{(aq)} + Ni_{(s)}$
→reactions would occur spontaneously
under standard state conditions.
a. $Ca_{(s)} + Cd^{2+}_{(aq)} \rightarrow Ca^{2+}_{(aq)} + Cd_{(s)}$
b. $2 Br-_{(s)} + Sn^{2+}(aq) \rightarrow Br_2_{(l)} + Sn_{(s)}$
c. $2Ag_{(s)} + Ni^{2+}_{(aq)} \rightarrow 2 Ag^+_{(aq)} + Ni_{(s)}$
Write working of $NICAD$ storage cell. Also write its applications.
→Aniline is less basic than ammonia. Explain.
Explain the trend in the density, melting and boiling points of Group 16 elements.