Question:
$\mathrm{KBr}$ is doped with $10^{-5}$ mole percent of $\mathrm{SrBr}_{2}$. The number of cationic vacancies in $1 \mathrm{~g}$ of $\mathrm{KBr}$ crystal is $10^{14}$. (Round off to the Nearest Integer).
[Atomic Mass : $\mathrm{K}: 39.1 \mathrm{u}, \mathrm{Br}: 79.9 \mathrm{u}$,
$\left.\mathrm{N}_{\mathrm{A}}=6.023 \times 10^{23}\right]$
Solution:
1 mole $\mathrm{KBr}(=119 \mathrm{gm})$ have $\frac{10^{-5}}{100}$ moles $\mathrm{SrBr}_{2}$
and hence, $10^{-7}$ moles cation vacancy
(as $1 \mathrm{Sr}^{2+}$ will result 1 cation vacancy)
$\therefore$ Required number of cation vacancies
$=\frac{10^{-7} \times 6.023 \times 10^{23}}{119}=5.06 \times 10^{14} \simeq 5 \times 10^{14}$
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- JEE Main
- Exam Pattern
- Previous Year Papers
- PYQ Chapterwise
- Physics
- Kinematics 1D
- Kinemetics 2D
- Friction
- Work, Power, Energy
- Centre of Mass and Collision
- Rotational Dynamics
- Gravitation
- Calorimetry
- Elasticity
- Thermal Expansion
- Heat Transfer
- Kinetic Theory of Gases
- Thermodynamics
- Simple Harmonic Motion
- Wave on String
- Sound waves
- Fluid Mechanics
- Electrostatics
- Current Electricity
- Capacitor
- Magnetism and Matter
- Electromagnetic Induction
- Atomic Structure
- Dual Nature of Matter
- Nuclear Physics
- Radioactivity
- Semiconductors
- Communication System
- Error in Measurement & instruments
- Alternating Current
- Electromagnetic Waves
- Wave Optics
- X-Rays
- All Subjects
- Physics
- Motion in a Plane
- Law of Motion
- Work, Energy and Power
- Systems of Particles and Rotational Motion
- Gravitation
- Mechanical Properties of Solids
- Mechanical Properties of Fluids
- Thermal Properties of matter
- Thermodynamics
- Kinetic Theory
- Oscillations
- Waves
- Electric Charge and Fields
- Electrostatic Potential and Capacitance
- Current Electricity
- Thermoelectric Effects of Electric Current
- Heating Effects of Electric Current
- Moving Charges and Magnetism
- Magnetism and Matter
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- Alternating Current
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