Case Study: Salts, POP, Bleaching Powder and Water of Crystallization

Read the following passage and answer the questions that follow:

Salts are formed by reactions of acids and bases. Strong acids react with strong bases to form neutral salts. Weak acids react with strong bases to form basic salts. Acidic salts are formed by strong acids and weak bases. $\text{Na}_2\text{CO}_3$ and $\text{NaHCO}_3$ are salts of strong base ($\text{NaOH}$) and weak acid ($\text{H}_2\text{CO}_3$). Bleaching powder is prepared when slaked lime reacts with dry chlorine gas. Crystalline salts are hydrated and lose water on heating. Gypsum on heating at $373\text{ K}$ gives Plaster of Paris.

What is the formula of POP (Plaster of Paris)? What is its chemical name?

Name the compound of sodium which is used for softening hard water. What is its chemical formula?

(I) What is water of crystallization? (II) Write the preparation of bleaching powder.

OR

(I) Name an indicator used by visually impaired children. (II) Give one use of bleaching powder.