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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