The compound MX (molar mass= 100 g mol-1) occurs in zinc blende structure. If rc= 80 pm and ra= 120 pm, its density will be

A
6.25 g cm^-3
B
8.11 g cm^-3
C
9.56 g cm^-3
D
10.4 g cm^-3

Solution:

We have $ρ = \frac{4 (M_{MX} / N_{A})}{{[4 (r_{a} + r_{c}) / \sqrt{3}]}^{3}} = \frac{3 \sqrt{3} (M_{MX} / N_{A})}{16 {(r_{a} + r_{c})}_{3}}$ $= \frac{(3 \sqrt{3}) [(120 g {mol}^{- 1}) / (6.022 \times 10^{23} {mol}^{- 1})]}{16 {[(120 + 80) \times 10^{- 10} cm]}^{3}}$ $= \frac{(3 \sqrt{3}) (20 \times 10^{- 23}) g}{16 \times 8.0 \times 10^{- 24} {cm}^{3}} = 8.11 g {cm}^{- 3}$

The compound MX (molar mass= 100 g mol^-1) occurs in zinc blende structure. If r_c= 80 pm and r_a= 120 pm, its density will be

Solution:

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