JEE Main 2014 · 6 Apr · Shift 1 · Chemistry Q33

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ChemistrySingle correct+4 / -1Question 33 of 90

CsCl crystallises in body centred cubic lattice. If 'a' is its edge length then which of the following expressions is correct ?

r_{\ce{Cs+}}+r_{\ce{Cl-}}=3a

r_{\ce{Cs+}}+r_{\ce{Cl-}}=\dfrac{3a}{2}

r_{\ce{Cs+}}+r_{\ce{Cl-}}=\dfrac{\sqrt3}{2}a

r_{\ce{Cs+}}+r_{\ce{Cl-}}=\sqrt3\,a

Answer and worked solution

Official answer: C

In CsCl, $\ce{Cs+}$ sits at the body centre and touches the $\ce{Cl-}$ ions at the corners along the body diagonal:
$2\left(r_{\ce{Cs+}}+r_{\ce{Cl-}}\right)=\sqrt3a\implies r_{\ce{Cs+}}+r_{\ce{Cl-}}=\frac{\sqrt3}2a.$

Topics:Crystal lattices and unit cells

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JEE Main 2014 · 6 Apr · Shift 1, Chemistry question 33