Chemical A is used for water softening to remove temporary hardness. A reacts with sodium carbonate to generate caustic soda. When ${\mathrm{CO}}_2$ is bubbled through a solution of A, it turns cloudy. What is the chemical formula of A$-$

(1) ${\mathrm{CaCO}}_3$                             

(2) $\mathrm{CaO}$

(3) $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$                           

(4) $\mathrm{Ca}{\left({\mathrm{HCO}}_3\right)}_2$

The first ionization energy value $\left(\mathrm{kJ}\right)$ ${\mathrm{mol}}^{-1}$ for $\mathrm{H},$ $\mathrm{Li},$ $\mathrm{F},$ $\mathrm{and}$ $\mathrm{Na}$ 

is given below but not in a correct order

$1681,$ $520,$ $1312,$ $495.$

The ionization energy value of H would be -

1. 1681                                 

2. 1312

3. 520                                   

4. 485

The hydrides ion ${\mathrm{H}}^{-}$ is a stronger base than its hydroxide ion ${\mathrm{OH}}^{-}$. Which of the following reactions will occur if sodium hydride $\left(\mathrm{NaH}\right)$ is dissolved in water –

(A) ${\mathrm{H}}^{-}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\to {\mathrm{H}}_3{\mathrm{O}}^{-}\left(\mathrm{aq}\right)$

(B) ${\mathrm{H}}^{-}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathcal{l}\right)\to {\mathrm{OH}}^{-}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right)$

(C) ${\mathrm{H}}^{-}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathcal{l}\right)\to \mathrm{No}<mspace\; width="1em"></mspace>\mathrm{reaction}$

(D) $\mathrm{None}<mspace\; width="1em"></mspace>\mathrm{of}<mspace\; width="1em"></mspace>\mathrm{these}$

Blackened oil planting can be restored into original form by the action of:

1. Chlorine

2. ${\mathrm{BaO}}_2$

3. ${\mathrm{H}}_2{\mathrm{O}}_2$

4. ${\mathrm{MnO}}_2$

Which of the following statement regarding ${\mathrm{H}}_2{\mathrm{O}}_2$ is wrong.

(1) It is stable in acid medium

(2) It acts as oxidising as well as reducing agent

(3) It has zero dipole moment

(4) Pure ${\mathrm{H}}_2{\mathrm{O}}_2$ is slightly acidic

Polyphosphates are used as water softening agents because they –

(1) form soluble complexes with anionic species

(2) precipitate anionic species

(3) form soluble complexes with cationic species

(4) precipitate cationic species

The ortho and para hydrogen have –

(A) Same physical properties but different chemical properties

(B) Different physical properties but same chemical properties

(C) Same chemical and physical properties

(D) Different physical and chemical properties

Permanent hardness of water can be removed, by adding –

(1) Soda lime

(2) Sodium bicarbonate

(3) Washing soda

(4) Sodium chloride

The correct increasing order of the acidity of ${\mathrm{CO}}_2,<mspace\; width="1em"></mspace>{\mathrm{H}}_2\mathrm{O}<mspace\; width="1em"></mspace>\mathrm{and}<mspace\; width="1em"></mspace>{\mathrm{H}}_2{\mathrm{O}}_2$ is $-$

(1) ${\mathrm{CO}}_2<{\mathrm{H}}_2{\mathrm{O}}_2<{\mathrm{H}}_2\mathrm{O}$                         

(2) ${\mathrm{H}}_2\mathrm{O}<{\mathrm{H}}_2{\mathrm{O}}_2<{\mathrm{CO}}_2$

(3) ${\mathrm{H}}_2\mathrm{O}<{\mathrm{H}}_2{\mathrm{O}}_2>{\mathrm{CO}}_2$                         

(4) ${\mathrm{H}}_2{\mathrm{O}}_2>{\mathrm{CO}}_2>{\mathrm{H}}_2\mathrm{O}$

Metal which does not react with cold water but evolves H₂ with steam is –

(1) Na                           

(2) K

(3) Pt                             

(4) Fe