In a face centred cubic lattice, atom A occupies the corner positions and atom B occupies the face centre positions. If one atom of B is missing from one of the face centred points, the formula of the compound is -
1. AB2
2. A2B3
3. A2B5
4. A2B
Select the correct option based on statements below:
Assertion (A): | In an hcp structure, each sphere is surrounded by eight other spheres. |
Reason (R): | ABC, ABC ................................ represents hcp structure. |
1. | Both (A) and (R) are true and (R) is the correct explanation of (A). |
2. | Both (A) and (R) are true but (R) is not the correct explanation of (A). |
3. | (A) is true but (R) is false. |
4. | Both (A) and (R) are false. |
Select the correct option based on statements below:
Assertion (A): | LiCl shows pink colour when heated in presence of lithium vapours. |
Reason (R): | LiCl shows Frenkel defect. |
1. | Both (A) and (R) are true and (R) is the correct explanation of (A). |
2. | Both (A) and (R) are true but (R) is not the correct explanation of (A). |
3. | (A) is true but (R) is false. |
4. | Both (A) and (R) are false. |
Select the correct option based on statements below:
Assertion (A): | Ferromagnetic solids become paramagnetic upon heating. |
Reason (R): | Unpaired electrons starts pairing upon heating. |
1. | Both (A) and (R) are true and (R) is the correct explanation of (A). |
2. | Both (A) and (R) are true but (R) is not the correct explanation of (A). |
3. | (A) is true but (R) is false. |
4. | Both (A) and (R) are false. |
An ionic compound has a unit cell consisting of A ions at the corners of a cube and B ions on the centers of the faces of the cube. The empirical formula for this compound would be :
1. AB
2. A2B
3. AB3
4. A3B
The formula of nickel oxide with metal deficiency defect in its crystal is . The crystal contains ions. The fraction of nickel existing as ions in the crystal is-
1. 0.96
2. 0.04
3. 0.50
4. 0.31
An element occurring in the bcc structure has unit cells. The total number of atoms of the element in these cells will be:
1.
2.
3.
4.
If an element (at. Wt. = 50) crystallises in fcc lattice, with a = 0.50 nm, then the density of unit cell if it contains 0.25 % Schottky defect is -
(Use )
1. 2.0 g/cc
2. 2.66 g/cc
3. 3.06 g/cc
4. None of the above.
Select the correct option based on statements below:
Assertion (A): | Crystalline solids have sharp melting points. |
Reason (R): | Crystalline solids have definite enthalpies of fusions. |
1. | Both (A) and (R) are true and (R) is the correct explanation of (A). |
2. | Both (A) and (R) are true but (R) is not the correct explanation of (A). |
3. | (A) is true but (R) is false. |
4. | Both (A) and (R) are false. |
An element has a body-centered cubic (BCC) structure with a cell edge of 288 pm. The atomic radius is:
1. pm
2. pm
3. pm
4. pm