IIT-JEE 2012 · Paper 1 · Chemistry Q24

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ChemistrySingle correct+3 / -1Question 24 of 60

A compound $\ce{M_pX_q}$ has cubic close packing (ccp) arrangement of X. Its unit cell structure is shown below. The empirical formula of the compound is

A cubic unit cell: X (shaded circles) at the 8 corners and 6 face centres (ccp); M (squares) at the body centre and at the middle of four edges (the four vertical edges as drawn).

\ce{MX2}

\ce{M2X}

\ce{M5X14}

Answer and worked solution

Official answer: B

X (ccp). 8 corners × $\frac18$ + 6 faces × $\frac12$ = 4.

M. 1 at the body centre + 4 edge centres × $\frac14$ = 2.

Formula. $\ce{M2X4}$ , i.e. $\ce{MX2}$ .

(B)

Topics:Crystal lattices and unit cells

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IIT-JEE 2012 · Paper 1, Chemistry question 24