Question

State the law of conservation of mass.

Answer 1

Hint: This law is based on the change in mass when a molecule reacts with another during a chemical reaction giving different products.

Complete step by step solution:
Statement: For any system closed to all transfers of matter and energy, the mass of the system must remain constant over time, as the system’s mass can-not change, so the quantity can neither be added nor removed.
This means that the total mass of reactants is always equal to the total mass of products in a physical change or chemical reaction.
This law is also called the law of indestructibility of matter. This means that matter is indestructible. The law was verified with Landolt’s experiment. He took solutions of NaCl and $$AgN{O}_3$$in two limbs of an H- shaped tube. The tube was sealed. Then the tube was shaken so that the solutions mix up resulting in a reaction as-

$$AgN{O}_3+NaCl\to AgCl+NaN{O}_3$$

After the reaction, the tube was weighed and it was found that the weight initially taken is equal to the weight of products. This verified the law.
We can have another example of the formation of a molecule of water. When we add one atom of Oxygen with mass 16 and two atoms of Hydrogen with mass 1 each, we get one molecule of $$H_{2}O$$with mass 18g. Thus, the mass is the same in both sides, reactants and products.

Note: Further, this law is not valid for nuclear reactions and radioactive disintegration. This is because during such reactions, a large amount of energy is released which results in a change in significant mass of reactants. Thus, the law of conservation of mass does not apply to such reactions. In such reactions, we assume that mass and energy both are conserved.