5. which quantities must be conserved in all chemical reactions?

In a chemical reaction, the quantities that must be conserved is Matter ( The law of conservation states matter cannot be created nor destroyed.) If the matter is conserved that means the reactants mass is the same as the product. So if matter is conserved, mass is conserved. Another quantity that must be conserved is the number of particles.
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In a chemical reaction, the mass and energy must be conserved, as it states in the law of conservation of mass and also energy. Matter cannot be created not destroyed. 

Wish i can but don’t know this