A crystalline solid of a pure substance has a face-centred cubic structure with a cell edge of 400 pm. If the density of the substance in the crystal is 8 g c m - 3 , then the number of atoms present

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A crystalline solid of a pure substance has a face-centred cubic structure with a cell edge of 400 pm. If the density of the substance in the crystal is 8 g c m - 3 , then the number of atoms present in 128 g of the crystal is

TestHub · Accepted Answer

d = Z × M a 3 × N A ⇒ M = a 3 × d × N A Z M = ( 400 ) 3 × 1 0 - 30 × 8 × N A 4 On solving M = 64 × 2 × 1 0 - 24 N A g Now, 64 × 2 × 1 0 - 24 N A g contains N A atoms 128 g will contain = N A 64 × 2 × 10 - 24 N A × 128 = 1 × 1 0 24

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