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 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
The crystal with a metal deficiency defect is -
1. NaCl
2. FeO
3. ZnO
4. KCl
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
The electrical conductivity of semiconductors increases with a rise in temperature because:
1. | Electrons jump from the valence band to the conduction band. |
2. | Electrons jump from the conduction band to the valence band. |
3. | No electrons jump from the valence band to the conduction band. |
4. | No electrons jump from the conduction band to the valence band. |
If NaCl is doped with mol% of , the number of cation vacancies will be -
1.
2.
3.
4. 2
Select the correct option based on statements below:
Assertion (A): | The stability of a crystal is reflected by the magnitude of its melting point. |
Reason (R): | Greater the intermolecular forces of attraction, the higher will be the stability and melting point of the substance. |
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. |
The packing efficiency of the face-centered cubic unit cell is:
(assuming that the atoms are touching each other)
1. 52.40 %
2. 68.04 %
3. 74 %
4. 79.06 %
Copper crystallizes into an fcc lattice with an edge length of 3.61 × 10−8 cm. The density of copper crystal will be -
1. 7.46 g cm-3
2. 9.67 g cm-3
3. 8.96 g cm-3
4. 5.63 g cm-3
A compound is formed by two elements M and N. The element N forms ccp and atoms of M occupy 1/3rd of tetrahedral voids. The formula of the compound would be -
1. MN
2. M3N4
3. M2N3
4. M3N2