A student was asked by his teacher to verify the law of conservation of mass in the laboratory. He prepared 5 % aqueous solutions of NaCl and `Na_(2)SO_(4)`. He mixied 10 mL of both these solutions in a conical flask. He weighed the flask on a balance. He then stirred the flask with a rod and weighed it after sometime. There was no change in mass. Read this narration and answer the following question
(i) Was the student able to verify the law of conservation of mass ?
(ii) If not, what was the mixtake committed by him ?
(iii) In your opinion, what he should have done ?
(iv) What is the value associated with it ?

Explanation

(i) No. he could not verify the law of conservation of mass inspite of the fact that there was no change in mass.
(ii) No chemical reaction takes place between NaCl and `Na_(2)SO_(4)`. This means that no reaction actually took place in the flask
(iii) He should have performed the experiment by using aqueous solutions of `BaCl_(2) and Na_(2)SO_(4)`. A chemical reaction takes place in this case and white precipitate of `BaSO_(4)` is formed.
(iv) In order to support or verify the law of conservation of mass in laboratory, one must select those substances which actually react chemically. Moreover, all chemical reactions involving gaseous species must be carried in close containers.