Procedure 2.3.a Preparation of Co2 aq Standard Solutions

Prepare five standard solutions (10 ml each) from the Co2+(aq) stock solution in clean, dry test tubes. The most concentrated will be the stock solution. The other four will be dilutions of the stock solution having concentrations between 0.040 and 0.085 M. Record your concentrations in the Results Summary section. 

You can easily prepare these standard solutions using only 10 and 5 ml graduated pipettes. Keep in mind a useful equation for preparing solutions C Vj = C2V2, where Ci is the concentration of your stock solution, Vx is the volume of stock solution that you use, C2 is the concentration of your final solution and V2 is the volume of your final solution (10 ml, which is V plus the volume of water added to dilute it). 

Keep in mind the importance of accuracy and precision in your use of the volumetric measurements you are making. The concentration of each standard solution should be known to three significant figures. The graduated pipettes should be read to + 0.02 ml. 

Securely seal each tube with parafilm to prevent any evaporation of the solvent. 

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