Rohit and Arun are two friends both of whom study in class IX in different schools. Earlier Rohit's mother used to purchase ordinary common salt for cooking food. But since the time Rohit had studied the benefits of using iodised common salt, the had made his mother purchase and use only iodised salt for cooking food. One day, while working in the kitchen, Rohit's mother mixed some ammonium chloride in iodised salt container by mistake. Rohit and Arun had recently studied the various method of separation of mixtures in the class. They started discussing the components and the method of separation of the mixture made by Rohit's mother unknowingly. Arun said that the mixture obtained by mixing ammonium chloride with iodised salt actually contains ammonium chloride, iodine and salt in it, so they had to use more than one method to separate this mixture into its components. Rohit, however, did not agree with Arun. He explained his point of view to Arun
(a) What are the benefits of using iodised salt ?
(b) What can you say about Arun's statement that the mixture obtained by mixing ammonium chloride and iodised salt contains ammonium chloride, iodine and salt ?
(c) Name and define the process which can be used for the separation of mixture containing ammonium chloride and iodised salt
(d) Describe briefly, how a mixture of ammonium chloride and iodised salt can be separated.
(e) What values are displyed by Rohit in this episode ?

Explanation

(a) The benefits of using iodised salt are as follows :
(i) Iodised salt provides iodine to thyroid gland for making thyroxine hormone which regulates metabolism, growth and development of the body. It also prevents 'goitre' disease
(ii) Iodised salt provides iodine which improves the functions of brain such as memory, concentration and the ability to lean
(b) Arjun's statement is not correct. This is because iodised salt does not contain free iodine element `(I_(2))`. Iodised salt usually contains iodine in the form of its salt, potassium iodide (KI). Moreover, iodised salt contains minute quantity of potassium iodide (which is only about 0.01 percent of salt)
(c) The mixture of ammonium chloride and iodised salt can be separated by the process of sublimation. The changing of a solid directly into vapours on heating, and of vapours into solid on cooling is called sublimation
(d) The mixture of ammonium chloride and iodised salt is heated in a china dish convered with an inverted funnel having a loose cotton plug at the top end. Ammonium chloride sublimes on heating and collects as a sublimate on the cold, inner walls of the inverted funnel. Iodised salt does not sublime, so it is left behind in the china dish
(e) The values displayed by Rohit in this episode are (i) Awareness of the composition of iodised salt (that it is mostly common salt with minute quantity of potassium iodide but no free iodine) (ii) Knowledge that ammonium chloride sublimes but common salt and potassium iodide present in iodised salt do not sublime (iii) Application of knowledge in solving everyday problems, and (iv) Concern for the health of his family (in enforcing use of iodised salt).