Generally, the first ionization energy increases along a period. But there are some exceptions. One which is not an exception is

• N and O

• Na and Mg

• Mg and Al

• Be and B

For alkali metals, which one of the following trends is incorrect?

• Hydration energy : Li > Na > K > Rb

• Ionization energy : Li > Na > K > Rb

• Density : Li < Na < K < Rb

• Atomic size : Li < Na < K < Rb

Which one of the following is true?

• NaOH is used in the concentration of bauxite ore

• NaOH is a primary standard in volumetric analysis

• Manganous hydroxide is soluble in excess of NaOH solution

• NaOH solution does not react with Cl

The reaction between sodium and water can be made less vigorous by

• adding a little alcohol

• amalgamating sodium

• adding a little acetic acid

• lowering the temperature

115.

Alkali metals have negative reduction potential and hence they behave as

• oxidising agents

• Lewis bases

• reducing agents

• electrolytes

The s-block element used as a catalyst in the manufacture of Buna-S rubber is

• Ca

• Ba

• Na

• Mg

When limestone is heated, CO₂ is given off. The metallurgical operation is

• smelting

• reduction

• calcination

• roasting

On heating potassium permanganate, one of the following compound is not obtained.

• O₂

• MnO

• MnO₂

• K₂MnO₄

Plaster of Paris is a white powder of formula :

• ${\mathrm{CaSO}}_4.\frac{1}{2}{\mathrm{H}}_2\mathrm{O}$

• CaSO₄.2H₂O

• CaSO₄.H₂O

• CaSO₄.$\frac{3}{2}$H₂O

CaC₂ + N₂ → A, product A is

• CaCN₂

• CaCN₂ and C

• CaCN₂ + N₂

• None of these