Question

Three students conducted experiments to verify the law of conservation of mass and the results they derived are as follows:
Student A: Used 6.3 g of Sodium carbonate and 15g of acetic acid as reactants and conducted verification in a conical flask. After the experiment the student realised that he got only 18g as the mass of products.
Student B: Used NaCl and water as reactants for verification. Even though there was no change in mass, his verification was not successful.
Student C: Conducted verification using barium chloride and sodium sulphate. He got a white ppt which he filtered and weighed. He did not get the desired result.

3a)Analyse the above situations and point out where each of the student went wrong.
b)Suggest two points, to keep in mind, while you carry out the verification.
c)Name the scientist who proposed the above law.

Answer 1

The analysis of the three students can be made as follows:

Explanation:

• 3a)  For the first student, the mistake was that he did the experiment in a conical flask and did not trap the carbon dioxide gas which was being released as a result of this experiment.

For the second experiment, the student B should have either constantly stirred the NaCL in water or should have heated the water, NaCL solution.

For the third mentioned experiment, the student did not collect the salts properly. He filtered and collected just one of them.

• 3b) Two points that should be kept in mind are:

1) Although the law of conservation of mass is accurate, yet one forgets that most of the mass might be converted into heat and one forgets to measure it.

2) Some mass might be lost in the form of a gas and one forgets to measure the gas.

• 3c) Antoine Lavoisier was the scientist who proposed the law of conservation of mass.