A chemical compound A is used for water softening to remove temporary hardness. A reacts with Na₂CO₃ to form caustic soda. When CO₂ is bubbled through A it becomes cloudy. The chemical formula of A is

(1) CaO

(2) Ca(OH)₂

(3) Ca(HCO₃)₂

(4) CaCO₃

CO₂ gas along with solid (y) is obtained when sodium salt (x) is heated. (x) is again obtained when CO₂ gas is passed into an aqueous solution of (y).  (x) and (y) are respectively-

1. Na₂CO₃. Na₂O

2. Na₂CO₃, NaOH

3. NaHCO₃, Na₂CO₃

4. NaCO₃, NaHCO₃

Which of the following statements regarding Be is incorrect?

(1) It forms ionic compounds almost exclusively, even with the highly electronegative elements

(2) It does not form ionic compounds containing simple Be²⁺ ion, but does readily achieve a maximum co-ordination number of four through formation of complex ions such as BeF₄ and [Be(H₂O)₄]²⁺

(3) It forms a series of organo derivatives BeR₂ and [BeR₃], which contain covalent Be-C bonds

(4) Its halides are covalent polymers that are readily hydrolysed or cleaved by donors

Which of the following represents probable order of mobility of ions in aqueous solution?

(1) Be²⁺<Mg²⁺<Na⁺<K⁺

(2) Be²⁺>Mg²⁺>Na⁺>K⁺

(3) Na⁺>K⁺>Be²⁺>Mg²⁺

(4) Na⁺<K⁺<Be²⁺<Mg²⁺

Which of the following order is correct?

Sodium carbonate exists as

(1) Na₂CO₃.10H₂O(s)

(2) Na₂CO_3.H₂O(s)

(3) Na₂CO₃

(4) In all forms its a matter of temperature

The pair of compounds that do not exist in solution together are:

1. NaHCO₃ and NaOH

2. NaHCO₃ and H₂O

3. NaHCO₃ and Na₂CO₃

4. Na₂CO₃ and NaOH

Among the following, the most basic oxide is                   

(1) Al₂O₃

(2) SiO₂

(3) P₂O₅

(4) Na₂O

While moving down the group (in alkaline earth metals) following property increases except

(1) Radius

(2) Solubility of hydroxides

(3) Solubility of sulphates

(4) Thermal stability of carbonates

$∆{\mathrm{H}}_{\mathrm{solution}}$ is positive for

I. LiF

II. CsI

III. RbF

IV. KF

(1) I, II, III & IV

(2) II only

(3) I only

(4) I & II only