KVPY SX SB Exam 2016 Question Paper

Question : 105 of 120

Marks: +1, -0

Copper (atomic mass = 63.5) crystallizers in a FCC lattice and has density 8.93 g.cm

^{ –3}

.
The radius of copper atom is closest to

Solution:

d={N×M}/{N_A×a^3}

8.93={4×63.5}/{6.023×10^23×a^3}

a^3 = 4.72 × 10^{–23}

a = (47.2 ×10^{–24})^{1/3}

= 3.61 × 10^{–8} \cm

= 3.61 ×10^{–10} \m

= 361 pm

a=2√2r

r=a/{2√2}=127.8

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