Chapter U1, Problem 15STP

Interpretation Introduction

Interpretation:

The correct statement for law of conservation of mass needs to be determined.

Concept introduction:

Mass cannot be created or destroyed in a chemical reaction.

In other words, the mass of any one element at the beginning of a reaction will equal to the mass of that element at the end of the reaction.

Total mass of reactant before reaction = Total mass of the product after reaction

Answer to Problem 15STP

option (A)

Explanation of Solution

In copper cycle, different steps are occur like addition of HNO₃ and addition of NaOH then addition of H₂SO₄ and finally addition of zinc. The end product is copper. Here mass of reactant after following so many steps is equal to the mass of product formed. This is because it is a cyclic reaction of copper.

Reason for correct option:

Copper cycle is a cyclic reaction and it follows the Law of conservation of mass. So, it can be proved that the mass of copper at the beginning of the reaction is equal to the mass of copper at the end of the reaction.

This is a cyclic reaction because it starts with substance copper and end with substance copper. So, this always follows the Law of conservation of mass. Thus, option (A) is correct.

Conclusion

Reasons for incorrect options:

(B) When there is a loss of mass in laboratory techniques it will not follow the Law of conservation of mass

(C) The Law of conservation of mass always states that there is no loss of mass in the series of experiment.

(D) The Law of conservation of mass is applicable to aqueous solution and gases solution also but it should be in isolated and in closed container.

Therefore, options (B), (C) and (D) are incorrect.