An element with density 11 . 2 g cm - 3 forms a FCC lattice with edge length of 4 × 10 - 8 cm . Calculate the atomic mass of the element ( N A = 6 . 02 × 10 23 ) .

Formula of density of the cubic crystal system is given by d = z × M a 3 × N A Where z is the number of atom per unit cell, M is the atomic mass of element, ' a ' is the edge length and N A is the Avogadro's number. Atomic mass, M = d × a 3 × N A z The effective number of atoms in FCC unit cell is 4 . M = ( 11 . 2 ) ( 4 × 10 - 8 ) 3 ( 6 . 023 × 10 23 ) 4 = 107 . 9 g mol - 1 .

An element with density 11 . 2 g cm - 3 forms a FCC lattice with edge length of 4 × 10 - 8 cm . Calculate the atomic mass of the element ( N A = 6 . 02 × 10 23 ) .

Formula of density of the cubic crystal system is given by d = z × M a 3 × N A Where z is the number of atom per unit cell, M is the atomic mass of element, ' a ' is the edge length and N A is the Avogadro's number. Atomic mass, M = d × a 3 × N A z The effective number of atoms in FCC unit cell is 4 . M = ( 11 . 2 ) ( 4 × 10 - 8 ) 3 ( 6 . 023 × 10 23 ) 4 = 107 . 9 g mol - 1 .

ZnO turns yellow on heating. Why?

In ZnO , Zn + 2 ions occupy the interstitial sites and electrons are trapped in the interstitial sites for neutralization. Crystals that show such type of defects are generally coloured. Zinc oxide is white in colour at room temperature. On heating, it loses oxygen and turns yellow.