Commonly used compounds for making chalks and other pottery articles is plaster of paris.  Its chemical formula is \((CaSO_4)_2.{1\over2}2H_2O\) onn partical losing water of crystallization by controlled heating of crystallization by controlled heating \(120^o-130^oC.\)  When \(CaSO_4.2H_2O\) is strongly heated it loses whole of water of crystallisation and gives anhydrous calcium sulphate.  Thus 'x' is \(CaSO_4.2H_2O\) is strongly heated it loses whole of water of crystallisation and gives anhydrous calcium sulphate.  Thus 'x' is \(CaSO_4.2H_2O;\) y is \(CaSO_4.{1\over2}H_2O\) and 'z' is \(CaSO_4.\)

\(2CaSO_4.2H_2O\xrightarrow{heat/120^o-130^o\ C}(CaSO_4)_2.{1\over2}H_2O+{3\over 2}H_2O(g)\)

\(2CaSO_4.2H_2O\xrightarrow{heat/>130^oC}CaSO_4\)

Sodium carbonate.

An acid molecule dissociates in an aqueous solution to produce H⁺ (or H₃,O⁺) ions and corresponding anions A. These free ions carry the electrical charge from one place to other, hence conduct electricity

(i) If H⁺ ion concentration is more, pH will be less and vice versa or pH of a solution is inversely proportional to H⁺ ion concentration or pH 52 log (H⁺).
(ii) This solution is neutral.
(iii) 1MNaOH solution.
(iv) When the pH in the mouth is below 5.5, bacteria present in the mouth produce acids by degradation of sugar and corrode the tooth enamel. It can be prevented by using tooth pastes which are generally basic.
(v) As hydronium [H₃O]⁺ ion.

The gas evolved at anode during electrolysis of brine is chlorine (G) When chlorine gas is passed through dry \(Ca(OH)_2\ (Y)\) produces bleaching powder (Z) used for disinfecting drinking water.
\(Ca(OH)_2+Cl_2\rightarrow CaOCl_2+H_2O\)
Since Y and Z are calcium salts, therefore X is also a calcium salt and is calcium carbonate.
\(CaCO_3+2HCl\rightarrow CaCl_2+CO_2+H_2O\)
\(Ca(OH)_2+CO_2 \rightarrow CaCO_3+H_2O\)

(i) Solid sodium chloride and conc.sulphuric acid
(ii) Dry litmus - no change
Wet blue litmus - changes to red
(iii) HCl+H₂O\(\rightarrow\)H₃O⁺+Cl^-

They react with metals to give out hydrogen gas.
e.g.,
Zn + 2HCI\(\rightarrow\)ZnCl₂+H₂
(ii) They react with bases to form salt and water. e.g.,
2NaOH +H₂SO₄\(\rightarrow\)Na₂SO₄+2H₂O
(iii) They react with metal carbonates to liberate CO₂ gas
Na₂CO₃+2HCl\(\rightarrow\)2NaCl+H₂O+CO₂

(i) Increase in the strength of alkali. So the nature of solution will be basic.
(ii) Hydroxide ion or hydroxyl ion or OH^- ion.
(iii) A paper impregnated with the universal indicator is generally used to measure the pH of a solution.