# For example, i am given a problem, how do ik if it' a diluton problem. I know that for dilution the concentration decreases and the volume increases?

Apr 26, 2015

The concentration decreases because the volume increases, if the number of moles is kept constant.

That's the key point to keep in mind when dealing with dilutions - the number of moles of solute remains unchanged.

When you dilute a solution, you essentially increase its volume while keeping the same amount of solute present. Since molarity is defined as moles per liters of solution, an increase in volume will mean a decrease in concentration.

The equation to use for dilution calculations is

${C}_{1} {V}_{1} = {C}_{2} {V}_{2}$, where

${C}_{1}$, ${V}_{1}$ - the concentration and volume of an initial solution;
${C}_{2}$, ${V}_{2}$ - the concentration and volume of the final solution;

A dilution problem will usually imply that you start with a solution that has a certain concentration and volume, and either add more solvent to that solution, or take a sample from it and add solvent to the sample.

Whatever the case may be, try to focus on moles of solute and keep an eye on how the volume changes.