Ionic bonding and lattice enthalpy
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See all →- What fraction of one edge centred octahedral void lies in one unit cell of fcc? Answer: 4. 1/4 Key idea: An octahedral void at an edge centre is shared by the 4 unit cells meeting at that edge. An fcc cell has one octahe... 1
- A compound is formed by two elements A and B. The element B forms cubic close packed structure and atoms of A occupy 1/3 of tetrahedral voids. If the formula of the compound is A_xB_y, then the value of x + y is in option Answer: 2. 5 Key idea: In ccp, if B atoms number N, there are N octahedral and 2N tetrahedral voids. Take 1 unit cell: B = 4 atoms; tetrahed... 1
- Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).Assertion (A) :In a particular point defect, an ionic solid is electrically neutral, even if few of its cations are missing from its unit cells.… Answer: 3. Both (A) and (R) are correct but (R) is not the correct explanation of (A) Key idea: missing cations with overall neutrality desc... 1
- Right option for the number of tetrahedral and octahedral voids in hexagonal primitive unit cell are : Answer: 4. 12, 6 Key idea: in a close-packed structure with n atoms per cell, there are n octahedral voids and 2n tetrahedral voids. A hexag... 1
- A compound is formed by cation C and anion A. The anions form hexagonal close packed (hcp) lattice and the cations occupy 75% of octahedral voids. The formula of the compound is : Answer: 3. C ₃ A ₄ In hcp, if there are N anions then there are N octahedral voids. Cations occupy 75% of octahedral voids, so cations = 0.7... 1
- Among CaH_2, BeH_2, BaH_2, the order of ionic character is Answer: 1. BeH ₂ < CaH ₂ < BaH ₂ Ionic character of a metal hydride increases with the electropositive (metallic) character of the metal, wh... 1