Among the following, the metal that can be used as an electrode in a photoelectric cell is- 

1.  Li   

2.  Na

3.  Rb 

4.  Cs

In the following reactions, A, B, and C are-

$\begin{array}{l}{\mathrm{NH}}_3+\mathrm{A}+{\mathrm{CO}}_2\to {\left({\mathrm{NH}}_4\right)}_2{\mathrm{CO}}_3\\ {\left({\mathrm{NH}}_4\right)}_2{\mathrm{CO}}_3+{\mathrm{H}}_2\mathrm{O}+\mathrm{B}\to {\mathrm{NH}}_4{\mathrm{HCO}}_3\\ {\mathrm{NH}}_4{\mathrm{HCO}}_3+\mathrm{NaCl}\to {\mathrm{NH}}_4\mathrm{Cl}+\mathrm{C}\end{array}$

1. $\mathrm{A}={\mathrm{O}}_2;<mspace\; width="1em"></mspace>\mathrm{B}={\mathrm{CO}}_2;<mspace\; width="1em"></mspace>\mathrm{C}={\mathrm{Na}}_2{\mathrm{CO}}_3$

2. $\mathrm{A}={\mathrm{H}}_2\mathrm{O};<mspace\; width="1em"></mspace>\mathrm{B}={\mathrm{O}}_2;<mspace\; width="1em"></mspace>\mathrm{C}={\mathrm{Na}}_2{\mathrm{CO}}_3$

3. $\mathrm{A}={\mathrm{H}}_2\mathrm{O};<mspace\; width="1em"></mspace>\mathrm{B}={\mathrm{O}}_2;<mspace\; width="1em"></mspace>\mathrm{C}={\mathrm{NaHCO}}_3$

4. $\mathrm{A}={\mathrm{H}}_2\mathrm{O};<mspace\; width="1em"></mspace>\mathrm{B}={\mathrm{CO}}_2;<mspace\; width="1em"></mspace>\mathrm{C}={\mathrm{NaHCO}}_3$

The metal mainly used in devising photoelectric cells is:
1.  Na
2.  Rb
3.  Li
4. Cs

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

Among the statements (I – IV), the correct ones are:

1. (I), (II), and (III)
2. (I), (II), and (IV)
3. (I), (III), and (IV)
4. (II), (III), and (IV)

An alkaline earth metal 'M' readily forms water-soluble sulphate and water-insoluble hydroxide. Its oxide MO is very stable to heat and does not have rock-salt structure. The alkaline earth metal M is-

1.  Mg 

2.  Be 

3.  Sr 

4.  Ca

Match the following compounds (Column I) with their uses (Column II):

Options:

The correct order of hydration enthalpies of alkali metal ions is -

1. $L{i}^{+}<mspace\; width="1em"></mspace>><mspace\; width="1em"></mspace>N{a}^{+}<mspace\; width="1em"></mspace>><mspace\; width="1em"></mspace>K^{+}<mspace\; width="1em"></mspace>><mspace\; width="1em"></mspace>R{b}^{+}<mspace\; width="1em"></mspace>><mspace\; width="1em"></mspace>C{s}^{+}$

2. $N{a}^{+}<mspace\; width="1em"></mspace>><mspace\; width="1em"></mspace>L{i}^{+}<mspace\; width="1em"></mspace>><mspace\; width="1em"></mspace>K^{+}<mspace\; width="1em"></mspace>><mspace\; width="1em"></mspace>R{b}^{+}<mspace\; width="1em"></mspace>><mspace\; width="1em"></mspace>C{s}^{+}$

3. $L{i}^{+}<mspace\; width="1em"></mspace>><mspace\; width="1em"></mspace>N{a}^{+}<mspace\; width="1em"></mspace>><mspace\; width="1em"></mspace>K^{+}<mspace\; width="1em"></mspace>><mspace\; width="1em"></mspace>C{s}^{+}<mspace\; width="1em"></mspace>><mspace\; width="1em"></mspace>R{b}^{+}$

4. $N{a}^{+}<mspace\; width="1em"></mspace>><mspace\; width="1em"></mspace>L{i}^{+}<mspace\; width="1em"></mspace>><mspace\; width="1em"></mspace>K^{+}<mspace\; width="1em"></mspace>><mspace\; width="1em"></mspace>C{s}^{+}<mspace\; width="1em"></mspace>><mspace\; width="1em"></mspace>R{b}^{+}$

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