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# Dilution Formula

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 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.

The only place to use this relationship is in the process of dilution or concentration of a solution.

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## Dilution Problems

Solved problems based on dilution are given below.

### Solved Examples

Question 1: A chemist requires 1.5M hydrochloric acid, HCl for a series of reactions. The only solution available is 6.0M HCl. What volume of 6.0M HCl must be diluted to obtain 5.0L of 1.5M HCl?
Solution:

Initial concentration of HCl Mi = 6.0M
Final concentration of HCl Mf = 1.5M
Final volume of solution Vf = 5.0L

The unknown is the initial volume Vi.

Substitute the values in the equation and rearranging the equation we get

Vi = $\frac{1.5M \times 5.0L}{6.0M}$ = 1.3L

To obtain the desired quantity of diluted HCl, the chemist should begin with 1.3L of the concentrated solution and add enough water to bring the volume up to 5.0L.

Question 2: If 500mL of a 15% v/v solution of methyl salicylate in alcohol is diluted to 1500mL, what is the percentage strength v/v?
Solution:

Substitute the given values in the equation to get the unknown value.

$\frac{1500mL}{500mL}$ = $\frac{15\%}{x\%}$ = 5%.

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