Answer:
No
Step-by-step explanation:
No, but the total mass of reactants must equal the total mass of products to be a balanced equation.
Example: Consider the following reaction ...
3H₂ + N₂ => 2NH₃ and 'amu' is atomic mass units (formula weights from periodic table)
In terms of molecules, there are 4 molecules on the left (3 molecular hydrogens (H₂) and 1 molecular nitrogen (N₂) and 2 molecules of ammonia on the right side of equation arrow. ∑reactant molecules ≠ ∑product molecules.
In terms of mass of reactants & mass of products, the 3H₂ + N₂ => 6amu + 28amu = 34amu & mass of products (2NH₃) => 2(14amu) + 6(1amu) = 34amu for sum of product masses.
∑mass reactants = ∑mass products <=> 34amu = 34amu.
The expression '∑mass reactants = ∑mass products' as applied to chemical equations is generally known as 'The Law of Mass Balance'.