A) \[2.57\times {{10}^{21}}\]
B) \[5.14\times {{10}^{21}}\]
C) \[1.28\times {{10}^{21}}\]
D) \[1.81\times {{10}^{21}}\]
Correct Answer: B
Solution :
[b]The molecular mass of NaCl \[=23+35.5=58.5g\] |
58.5 g of NaCl contains \[=6.023\times {{10}^{23}}\] molecules |
1 g of NaCl contains \[=\frac{6.023\times {{10}^{23}}}{58.5}\] |
\[=1.02\times {{10}^{22}}\] molecules |
and 2 g of NaCl contains \[=\frac{6.023\times {{10}^{23}}\times 2}{58.5}\] |
\[=2.05\times {{10}^{22}}\] molecules |
Now, each unit cell of a face centered cubic unit cell contains 4 molecules of NaCl. |
\[\therefore \] Number of unit cells present in \[2g=\frac{2.05\times {{10}^{22}}}{4}\] |
\[=5.14\times {{10}^{21}}\] unit cells of NaCl |
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