Question

Salts play a very important role in our daily life. Sodium chloride which is known as common salt is used almost in every kitchen. Baking soda is also a salt used in faster cooking as well as in baking industry. The family of salts is classified on the basis of cations and anions present in them.

1. Identify the acid and base from which Sodium chloride is formed.   1
2. Find the cation and the anion present in Calcium sulphate.   1
3. "Sodium chloride and washing soda both belong to the same family of salts." Justify this statement.   2
                                                    OR
   Define the term pH scale. Name the salt obtained by the reaction of Potassium hydroxide and Sulphuric acid and give the pH value of its aqueous solution.   2

Answer 1

1. The acid is hydrochloric acid \[\ce{(HCI)}\], and the base is sodium hydroxide \[\ce{(NaOH)}\].
   \[\ce{HCl + NaOH → NaCl + H2O}\]
2. Calcium sulphate \[\ce{(CaSO4)}\] consists of the cation calcium \[\ce{(Ca2+)}\] and the anion sulphate \[\ce{(SO^2-_4)}\].

3. Both sodium chloride (NaCl) and washing soda (Sodium carbonate, \[\ce{Na2CO3.10H2O)}\] belong to the Sodium family of salts, which contain sodium as a cation. Washing soda is made from sodium chloride. The reaction is given below:
   \[\ce{NaCl + NH3 + H2O + CO2 -> \underset{Sodium hydrogen carbonate}{NaHCO3} + NH4Cl}\]
   \[\ce{2NaHCO3 ->[Heat] Na2CO3 + CO2 + H2O}\]
                                        OR
   pH Scale: The pH scale is a logarithmic scale used to measure the acidity or basicity of aqueous solutions. It monitors the concentration of hydrogen ions \[\ce{(H+)}\] in a solution. The pH scale ranges between 0 and 14, where:

   • pH less than 7 indicates acidity,
   • pH equal to 7 indicates neutrality and
   • pH greater than 7 indicates alkalinity or basicity.
     The reaction of potassium hydroxide \[\ce{(KOH)}\] and sulphuric acid \[\ce{(H2SO4)}\] produces potassium sulphate \[\ce{(K2SO4)}\]. The pH of the aqueous solution will be close to 7, suggesting neutrality.