Two elements A and B have similar chemical properties. They don't form solid hydrogencarbonates, but react with nitrogen to form nitrides. A and B, respectively, are :

1. Na and C

2. Li and Mg

3. Cs and Ba

4. Na and Rb

Magnesium powder burns in air to give-

1. MgO only

2. MgO and Mg(NO₃)₂

3.  MgO and Mg₃N₂

4.  Mg(NO₃)₂ and Mg₃N₂

The INCORRECT statement is :

1. Lithium is least reactive with water among the alkali metals

2. LiCl crystallises from aqueous solution as LiCl.2H₂O

3. Lithium is the strongest reducing agent among the alkali metals

4. LiNO₃ decomposes on heating to give LiNO₂ and O₂

The products obtained on heating LiNO₃ will be:

1. ${\mathrm{Li}}_2\mathrm{O}+{\mathrm{NO}}_2+{\mathrm{O}}_2$

2. ${\mathrm{Li}}_3\mathrm{N}+{\mathrm{O}}_2$

3. ${\mathrm{Li}}_2\mathrm{O}+\mathrm{NO}+{\mathrm{O}}_2$

4. ${\mathrm{LiNO}}_2+{\mathrm{O}}_2$

The best description of the change that occurs when Na₂O(s) are dissolved in water is-

1. Oxide ion accepts a shared pair of electrons

2. Oxide ion donates a pair of electrons

3. Oxidation number of oxygen increases

4. Oxidation number of sodium decreases