Question

Potassium distance 4.525 Å. Its molecular weight is 39. Its density in kg/m³ is.

• A. 900
• B. 494
• C. 602
• D. 802

Answer 1

Answer: (A)

900

Answer 2

Density $\rho = \frac{nA}{N(a)^{3}}$

where n = 2 for bcc structure , A = 39 × 10^–3 kg,

N = 6.02 × 10²³, a $= \frac{2}{\sqrt{3}}d = \frac{2}{\sqrt{3}} \times (4.525 \times 10^{- 10})m$

(d = nearest neighbour distance = distance between centres of two neighbouring atoms $= \frac{a}{\sqrt{2}}$)

On putting the values we get ρ = 907