9.9%
|Approximate Value − Exact Value| divided by
|Exact Value| X 100
Explanation:
According to the law of conservation of mass, mass can neither be created nor destroyed but it can simply be transformed from one form to another.
For example, 
Mass of Na = 23 g/mol
Mass of Cl = 35.5 g/mol
Sum of mass of reactants = mass of Na + mass of Cl
= 23 + 35.5 g/mol
= 58.5 g/mol
Mass of product formed is as follows.
Mass of NaCl = mass of Na + mass of Cl
= (23 g/mol + 35.5) g/mol
= 58.5 g/mol
As mass reacted is equal to the amount of mass formed. This shows that mass is conserved.
As a result, law of conservation of mass is obeyed.
No, there’s not any pressure
The reason does FeCl3 serve in the electrophilic sweet-smelling substitution response amongst chlorine and benzene is that it fills in as a Lewis corrosive impetus by responding with the Cl2 and along these lines actuates it toward assault by benzene's π electrons.