On heating Al at in air, is formed. The reaction is:
1. an endothermic reaction
2. an exothermic reaction
3. reduction of aluminium
4. none of the above
Alumina on heating with carbon in nitrogen atmosphere gives:
1.
2.
3.
4.
Hoope's process is used in the refining of:
1. Al
2. Zn
3. Ag
4. Cu
The correct order of decreasing hardness of the following compounds is:
1. Diamond > Borazon > Carborundum > Corundum
2. Borazon > Diamond > Carborundum > Corundum
3. Corundum > Carborundum > Borazon > Diamond
4. none of the above
Aluminium becomes passive in nitric acid because it-
1. Is a noble metal
2. Forms a thin film of oxide
3. Has a positive reduction potential
4. None of the above
Chemically thermite is -
1. Fe and Al
2. Ferric oxide and aluminium powder
3. Barium peroxide and magnesium powder
4. Cu and aluminium
formation involves large quantity of heat evolution which makes its use in:
1. deoxidizer
2. confectionary
3. indoor photography
4. thermite welding
Al and Ga have the same covalent radii because of:
1. Greater shielding power of s-electrons of Ga atoms
2. Poor shielding power of s-electrons of Ga atoms
3. Poor shielding power of d-electrons of Ga atoms
4. Greater shielding power of d-electrons of Ga atoms
Which is used as mordant?
1.
2.
3.
4.
Hybridisation of boron in diborane is:
1.
2.
3.
4.