1. Some basic concept of chemistry — Chemistry STD 11 Science — Question

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When we balance an equation, we determine the ratio of reactants to products which allows for the total number of atoms of reactants to match the number of atoms of the products.

Since the type of atoms does not change and the number of atoms stays that same, the total mass that goes into the chemical change will match the mass that comes out after the change.

So, law of conservation of mass is the correct answer.