Law of conservation of mass to explain why a chemical equation must be balanced?

Law of conservation of mass state that mass can neither be created nor be destroyed.  Also chemical reaction of the sum is outlined in The Law Of Conservation of Matter.

Explanation:

In a chemical reaction the sum of the masses of the products will be equal to the sum of the masses of the reactants. Thus a chemical reaction conserves the total mass. For this law to be valid the system where the reactions take place should be closed.

It has to be properly ensured that there is no transfer of energy or mass between the system and its outer environment. If that happens the sum of masses of products differs from that of the reactants due to the gain or loss of matter to surroundings.  

answer: the value of enthalpy change will be -152.80 kj.

solution:

pressure = 1atm , temperature = = 298 k

given that pressure and temperature are same in both gases , the number of moles of both gases can be determined by the ideal gas equation.

according to reaction 3 moles no are reacting with 1 mol of ,then 0.49 mol of no will react with moles of ozone that is 0.16 moles of ozone. since, no is limiting reagent and is an excessive reagent.

enthalpy change for the reaction between the given volumes of the gases is :

i think   the answer is c hope i'm right