Rahul burnt 3kg of fire wood got only 500 g of ashes and says that Law of conservation of mass is not valid do you agree or disagree

disagree

Explanation:

Cellulose (main component of wood beside lignin) is composed from carbon, hydrogen and oxygen with the following molecular formula (C₆H₁₀O₅) ₓ (where x is the degree of condensation of beta-glucose units which are the basic monosaccharide of the cellulose polysaccharide).

Now when you burn cellulose you obtain carbon (ashes), carbon dioxide (CO₂) and water (H₂O). Of course, beside the main products we may have other by-products but we consider them in very low quantity.

The difference between 3 kg of starting wood and 500 g of ashes is representing the quantity of carbon dioxide (CO₂) and water (H₂O) formed.

We have to say that CO₂ and H₂O are in gaseous state and escape in the atmosphere.

The law of conservation of mass is always valid.