Ionic Compounds and Radius Ratios

Q.

A compound forms hexagonal close-packed structure. What is the total number of voids in 0.5 mol of it? How many of these are tetrahedral voids?

Q. $KCl$ crystallises in the same type of lattice as $NaCl$. Given that $r_{N{a}^{+}}/r_{C{l}^{-}}=0.50$ and $r_{N{a}^{+}}/r_{K^{+}}=0.70$, calculate the ratio of the side of the unit cell of $KCl$ to that of $NaCl$:

1. 1.143
2. 1.224
3. 1.414
4. 0.875

Q.

What do we mean by radius ratio?

1. Ratio of coordination number to radius of Z_eff

2. Ratio of radius of anion to radius of cation.

3. Ratio of radius of cation to radius of anion.

4. Ratio of Zeff to coordination number.

Q. ${\left[Si{F}_6\right]}^{2-}$ is known whereas ${\left[SiC{l}_6\right]}^{2-}$ not. Give possible reasons.

Q. $N{a}_{2}O$ has antifluorite structure. In $N{a}_{2}O,$ the coordination number of $N{a}^{+}\text{and}{O}^{2-}$ are, respectively:

1. 4, 4
2. 6, 6
3. 8, 4
4. 4, 8

Q. Pick out the incorrect statement about $CsCl$ structure.

1. $CsCl$ has a bcc structure
2. $C{l}^{-}$ adopts a simple cubic lattice
3. Coordination no. of both $C{s}^{+}$ and $C{l}^{-}$ is 6
4. $C{l}^{-}$ ions are present at cubic centres

Q. In closest packing of atoms

1. The size of tetrahedral void is greater than that of the octahedral void

2. The size of the tetrahedral void is smaller than that of the octahedral void.

3. The size of tetrahedral void is equal to that of the octahedral void.

4. The size of tetrahedral void may be larger or smaller or equal to that of the octahedral void depending Upon the size of atoms.

Q.

If the radius ratio is between 0.225 - 0.414, what will be the type of void present. What will be the coordination number?

1. tetrahedral - 4

2. tetrahedral - 2

3. octahedral

4. linear

Q.

Compare the alkali metals and alkaline earth metals with respect to (i) ionization enthalpy (ii) basicity of oxides and (iii) solubility of hydroxides.

Q. For an ionic crystal of the general formula AX and coordination number 6, the value of radius ratio will be

1. Greater than 0.73
2. Less than 0.22
3. In between 0.41 and 0.22
4. In between 0.73 and 0.41

Q. In sodium chloride, $C{l}^{-}$ ions form ccp arrangement. Which site will $N{a}^{+}$ ions occupy in this structure?

1. Cubic
2. Tetragonal
3. Octahedral
4. Trigonal bipyramidal

Q.

If the radius ratio is between 0.414 - 0.732, what will be the type of void present? What will be the coordination number?

1. Tetrahedral - 4

2. Octahedral - 6

3. Cubic - 8

4. Linear - 2

Q. Select the incorrect statement for a $CsCl$ crystal:

1. Coordination number for $C{s}^{+}$ and $C{l}^{-}$ is 6
2. $\frac{r_{C{s}^{+}}}{r_{C{l}^{-}}}\ge 0.732$
3. The structure changes to $NaCl$ type at $760\text{K}$
4. $C{l}^{-}$ ions are present at cubic sites

Q. Which of the following figure represent the tetrahedral void?
(note: red spheres are places over the layer of black spheres)

1. 
2. 
3. 
4. 

Q. An ionic compound AB has ZnS type of structure, if the radius A+ is 22.5pm, then the ideal radius of B- is

1. 54.35pm

2. 145.16pm

3. 100pm

4. None

Q. The coordination number in hcp is:

1. $6$
2. $12$
3. $18$
4. $24$

Q. A crystal of lead $\left(II\right)$ sulphide has a $NaCl$ structure. In this crystal, the shortest distance between a $P{b}^{2+}$ ion and $S^{2-}$ ion is $297\text{pm}$. What is the volume of unit cell in lead sulphide?
(Given, $(594{)}^3=209584584$)

1. $209.6\times {10}^{-24}{\text{cm}}^3$
2. $207.8\times {10}^{-23}{\text{cm}}^3$
3. $22.3\times {10}^{-23}{\text{cm}}^3$
4. $209.8\times {10}^{-23}{\text{cm}}^3$

Q. Iron$\left(\text{II}\right)$oxide crystallise in cubic structure with unit cell edge length of $5A^{\circ }$. If the density of oxide is $3.8{\text{g cm}}^{-3}$. Calculate the number of $F{e}^{2+}$ ions present in each unit cell.
[ Molar mass of $Fe=56\text{g/mol}$ ]

1. $1$
2. $2$
3. $3$
4. $4$

Q. In which of the following pairs, the cations occupy, same type of site?

1. $CsCl,$ Zinc blende $\left(ZnS\right)$
2. $NaCl,CsCl$
3. $N{a}_{2}O,Ca{F}_2$
4. Zinc blende $\left(ZnS\right),N{a}_{2}O$

Q. The coordination number of cation and anion in flourite $Ca{F}_2$ and anti-flourite $N{a}_{2}O$ are respectively:

1. $8:4$ and $6:3$
2. $6:3$ and $4:4$
3. $8:4$ and $4:8$
4. $4:8$ and $8:4$

Q. The oxidation state of the central atom in the anion of the compound $Na{H}_{2}P{O}_2$ will be:

1. $-3$
2. $+1$
3. $+3$
4. $+5$

Q. If the value of ionic radius ratio $\left(\frac{r_c}{r_a}\right)$ is 0.52 in an ionic compound, the geometrical arrangement of ions in crystal is

1. Planar
2. Tetrahedral
3. Octahedral
4. Pyramidal

Q. $TiCl$ has the structure similar to $CsCl,$ the coordination number of $T{i}^{+}$ is -

1. 4
2. 6
3. 10
4. 8

Q.
What is the absolute configuration of the given chiral carbon?

1. R
2. S
3. Both
4. None

Q.

The CsCl type structure is exhibited by alkali halides only when the radius of the cation is large enough to keep touching its eight nearest neighbour anions. Below what minimum ratio of cation to anion radii $\left(\frac{r_{+}}{r_{-}}\right)$ this contact is prevented ?

1. 0.414

2. 0.632

3. 0.732

4. 0.225

Q. In trigonal or rhombohedral unit cell only gamma is not equal to 90 degree or all three angles alpha beta and gamma are not equal to 90 degree

Q. if the ratio of radius of cation and radius of anion is equal to 0.255 then in which void( trigonal or tetrahedral) will these cations accommodate?

Q.

How many tetrahedral voids will be formed, if 2n Octahedral voids are formed in the cubic close packing?

1. 8n

2. 6n

3. 2n

4. 4n

Q. Which of the following is/are correct regarding Crystal Field Theory (CFT) ?

1. In an isolated gaseous metal ion, five d orbitals are degenerate
2. In an isolated gaseous metal ion, no d orbitals are degenerate
3. If a spherically symmetrical​ field of ligands surrounds ​the metal atom/ion, degeneracy is lost
4. If a spherically symmetrical​ field of ligands surrounds ​the metal atom/ion, this degeneracy ​is still maintained.​

Q. Calcium crystallises in a face centred cubic unit cell .The volume of unit cell is $1.72\times {10}^{-22}c{m}^3$. What will be its density $\left(ingc{m}^{-3}\right)$ if it contains $0.5\%$ of Schottky defect?

1. $0.44$
2. $3.57$
3. $1.53$
4. $2.88$