One of the most common procedures encountered in any science laboratory is dilution, the process in which solvent is added to a solution to decrease the concentration of the solute. In dilution the amount of solute does not change.
Dilution is the process of decreasing the concentration of a solute in a solution, usually simply by mixing with more solvent like adding more water to a solution. To dilute a solution means to add more solvent without the addition of more solute. The resulting solution is thoroughly mixed so as to ensure that all parts of the solution are identical.
"The number of moles of solute is the same before and after dilution."
The only place to use this relationship is in the process of dilution or concentration of a solution.
The Dilution Formula can be used where there is only one solute present, if a reaction is taking place the problem must be approached as a stoichiometry problem.