For the chemical reactiom to be at equilibrium:
1- The rate of forward reaction must be equal to the rate of the reverse reaction.
2- The mass of EACH element must be equal before and after the reaction (no NET change in mass), otherwise the equilibrium will shift.
Important note: you need to check the mass of each element before and after the reaction (i.e, reactants side and products side) and the not the mass of the system as a whole. This is because the mass of the whole system will be preserved whether the system is at equilibrium or not (this is the fundamental law of mass conservation)
The last set which is n=4 l=3 m=3 is a valid set
Answer:-
atoms.
Solution:- We have been given the grams of carbon tetrachloride and asked to calculate the number of atoms of chlorine. It is a three step conversion problem. In the first we convert the grams of carbon tetrachloride to moles of it. In second step we convert moles of carbon tetrachloride to moles of chlorine and in the third step we convert the moles of chlorine to atoms of chlorine.
For grams to mole conversion we need the molar mass of the compound. Molar mass of carbon tetrachloride is 153.82 grams per mol. If we look at the formula of carbon tetrachloride then four chlorine are present in it. It means 1 mol of carbon tetrachloride has four moles of chlorine. The calculations are as follows:

=
atoms
So, there are
atoms in 12.2 grams of
.