Solutions & Solubility Solution Preparation by dilution

Review  Standard Solution = a solution for which the precise concentration is known  Used in research laboratories and industrial processes  Used in chemical analysis and precise control of chemical reactions

Preparing a Solution by Dilution  Dilution = the process of decreasing the concentration of a solution, usually by adding more solvent  Stock Solution = a solution that is in stock or on the shelf (i.e., available); usually a concentrated solution

 Equipment needed to prepare a standard solution:  Graduated Pipettes and bulbs  Volumetric flask Solution Preparation

Graduated & Volumetric Pipettes and Bulb transfer small quantities of liquid

The Formula  the number of moles (n) does not change when more solvent is added to a solution; only the concentration changes  therefore, n i (initial) = n f (final)  If a solution is diluted from V 1 to V 2, the molar concentration of that solution changes according to the following equation:  C 1 V 1 = C 2 V 2  ** remember: n = C X V **

The Variables C 1 V 1 = C 2 V 2  C 1 = initial concentration of stock solution  V 1 = volume of stock solution to be transferred  C 2 = final concentration of dilute solution  V 2 = final volume of dilute solution

Example  How do you prepare 250 mL of a 0.01 mol/L solution from a stock solution of 0.1 mol/L?  The Calculations: C 1 V 1 = C 2 V 2

The Procedure  Remove the calculated V 1 amount of your stock solution using a pipette.  Place that volume into a clean, dry volumetric flask of the volume needed for your diluted solution  Add distilled water to the mark of the volumetric flask  Label the flask with the new solution concentration

Now you try….  Make 50.0mL of 0.150M NaCl solution from your 0.300M stock solution