How many unit cells are present in a cube shaped ideal crystal of NaCl of mass 1g?
Utsab Bora , 8 Years ago
Grade 12th Pass
Physical Chemistry> How many unit cells are present in a cube...
3 Answers
Beenu Mathew
Last Activity: 8 Years ago
HI,
we all know the equation
d= Z * M/a3 * Na
Now,
the twist....are you ready
d* a3 = Z * M/Na
what is d * a3 ….well....IT IS THE MASS OF 1 UNIT CELL
SO,
now...
we know NaCl has a mass of 35.5g
and Z=4
so,
mass of 1 unit cell= 4*35.5/Na
= 142/Na
Number of unit cells = 10g* Na/142
finally you will get an answer of approx
4.2 * 1022 unit cells
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Ranjan Choudhary
Last Activity: 7 Years ago
using eqn,
d= Z * M/a3 * Na
or
d* a3 = Z * M/Na
d * a3 …..IT IS THE MASS OF 1 UNIT CELL
One unit cell of NaCl contains 4 NaCl units (ie)
we know NaCl has a mass of 58.5g
mass of 1 unit cell= 4*58.5/Na
= 234/Na
Number of unit cells = 1g* Na/234=2.57 *10^21⇒2.57×1021⇒2.57×102
Arbaz khan
Last Activity: 6 Years ago
Molar mass of NaCl=58.5
We knw in a unit cell we have 4 formula mass of NaCl, so z=4
d=z*M/a^3*Na
d*a^3=z*M/Na
We know mass=density *vol. => m=d*a^3
This mass represnts mass of 1 unit cell.
Then unit cell mass=4*58.5/N
Then unit cell in 1g of NaCl crystal=mass of
crystal/mass of unit cell
=1/4*58.5*Na => 6*10^23/234 = 2.57*1021 ans.
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