Pre-lab 2.4.a Acid-Base Titrations of Solutions Containing

Pre-lab 2.4.a Acid-Base Titrations of Solutions Containing Two Acids17 

In this experiment, we wish to accurately measure the amount of NH3 that is released from a known amount of cobalt ammine complex. To do so, the released NH3 is delivered into a beaker containing a known excess amount of strong acid, HC1. The reaction of NH3 with HC1 quantitatively introduces the second weaker acid, NH4+, into the solution, equation (2.8). 

By choosing an indicator suitable for the first HC1 equivalence point, bromcresol green (pH range 3.8-5.4), one can determine by titration with a strong base the amount of HC1 present in solution following the reaction with the NH3 that was released from the metal complex. In summary, the total HC1 added to the solution minus that determined to be in solution by titration is equal to the NH4+, equation (2.9) 

Safety warning Operations set off between the lines must be performed in a fume hood. 

Pipet 10 ml of 1.0 M HC1 into a 125 ml beaker and add approximately three drops of 

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