The Solid State

Question 265
CBSEENCH12010359

What type of magnetism is shown by a substance if magnetic moments of domains are arranged in same direction?

Solution

When the magnetic moments of domains are arranged in the same direction then, the substance shows ferromagnetism.

Question 266
CBSEENCH12010372

An element crystallizes in a f.c.c. lattice with cell edge of 250 pm. Calculate the density if 300 g of this element contain 2 × 1024 atoms.

Solution
We space have space given colon
straight a equals space 250 space pm space equals space 250 space straight x space 10 to the power of negative 12 end exponent straight m
straight z equals space 4
straight m equals 300 straight g
straight m equals space straight M over straight N subscript straight A space left parenthesis where space straight M space is space molar space mass right parenthesis

straight M space equals space fraction numerator 300 space straight x space 6.02 space straight x space 10 to the power of 23 over denominator 2 space straight x space 10 to the power of 24 end fraction space equals space 90.3 space straight g divided by mol

Density comma space straight d equals fraction numerator space zM over denominator straight a cubed straight N subscript straight A end fraction

straight d space equals space fraction numerator 4 space straight x space 90.3 over denominator left parenthesis 250 right parenthesis cubed space straight x space 10 to the power of negative 36 end exponent space straight x space 6.02 space straight x space 10 to the power of 23 space end fraction space equals space 38.4 space straight g divided by space cm cubed

density space equals space 38.4 space straight g divided by cm cubed
Question 267
CBSEENCH12010386

Given an example each of molecular solid and an ionic solid.

Solution

(i)  Molecular Solid   - I2

(ii)  Ionic Solid  - NaCl

Question 268
CBSEENCH12010406

An element crystallizes in b.c.c lattice with cell edge of 500 pm. The density of the element is 7.5g cm-3. How many atoms are present in 300 g of the element ?

Solution

We have given,
a= 500pm
d=7.5 g cm-3
mass = 300g
by space using space formula comma
fraction numerator straight z space xM over denominator straight a cubed space straight x space straight N subscript 0 end fraction space equals space straight d

straight N subscript 0 space equals space fraction numerator straight z space xM over denominator straight a cubed space straight x space straight d end fraction

straight N space equals space fraction numerator 2 space straight x space 300 straight g over denominator space left parenthesis 5 space straight x 10 to the power of negative 8 end exponent space cm right parenthesis cubed space straight x space 7.5 end fraction

straight N space equals space 6.4 space straight x space 10 to the power of 23 space atoms

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