Question

The chemical reaction shown above takes place in a closed system. What is true about the system while the reaction occurs? A. The total number of particles in the system decreases. B. The total mass of the particles in the system stays the same. C. The total mass of the particles in the system increases. D. The total number of particles in the system increases.

Answer 1

Answer: In a chemical reaction, the total mass of the particles in the system stays the same

Explanation:

Law of conservation of mass states that mass can neither be created nor be destroyed but it can only be transformed from one form to another form.  

This also means that total mass on the reactant side must be equal to the total mass on the product side in a chemical reaction.

Every balanced chemical reaction follows law of conservation of mass.

For Example: Formation of water molecule

$2H_2+O_2\rightarrow 2H_2O$

Total mass on reactant side = $[2(2\times 1)+(2\times 16)]=36g/mol$

Total mass on product side = $[2((2\times 1)+16)]=36g/mol$

Hence, in a chemical reaction, the total mass of the particles in the system stays the same