KVPY SX SB Exam 05-Nov-2017 Question Paper

Question : 59 of 120

Marks: +1, -0

A mineral consists of a cubic close-packed structure formed by O

^{2–}

ions where half the octahedral voids are occupied by Al

^{3+}

and one-eighth of the tetrahedral voids are occupied by Mn

^{2+}

. The chemical formula of the mineral is

Solution:

No of O

^{–2}

per unit cell =

8×1/8+6×1/2=4

No of Al

^{+3}

per unit cell

= 4 × 1/2 = 2

No of Mn

^{+2}

per unit cell

= 8 × 1/8 = 1

MnAl_2O_4

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