Titration

First things first. What is titration? Titration is the process of adding a solution of known concentration, to a solution with a known volume, but a unknown concentration. The solution with known concentration(which we could also call a tirant if we wanted to be scientific), is added until the reaction reaches neutralization. We know when a reaction is neutralized because it is indicated by a color change.  The substance that indicates this color change is a Ph indicator. The titration process is fairly simple. The experiment usually goes in the following steps:

1. Clean all materials with distilled water.

2.Measure out precise amount of unknown solution, or your acid(this can be the most difficult part of the experiment)! Transfer this into a Erlenmeyer flask ( they are more precise and accurate than beakers).

3.  Now, you add 3 or 4 drops of the Ph indicator into the flask.

4. Place the flask on a stirrer, and place a white “flea” (magnet) into the flask. Turn the stirrer on to spin the “flea”. This is to ensure that all of the solution and Ph are mixed.

5. Now comes the fun part. Start filling the flask with some of the known solution (your base).  Make sure you measure how much base was in the buret before you start pouring it into the acid.

6. Once the solution changes color, it has been completely neutralized.  This means you can stop adding the base.

7. Now you can measure how much base is left in the buret, and determine how  much was used.

8. Finally, you can plug this new information into the equation M1V1=M2V2

In M1V1=M2V2,  M1 and M2 are the initial and final molarities. V1 and V2 are the initial and final volumes. So you just plug in the amount of solution you had  when you began ( V1) times the Molarity of the known solution (M1). Set it equals to the amount of solution in the buret after you were finished (V2) to find the Molarity of the unknown solution(M2).

Now, we can use these steps to determine  the concentration of an antacid tablet composed of magnesium bicarbonate. You could use Hydrochloric acid as your acid.

1. Clean the equipment. Fill the buret with an exact amount of HCL solution. Make sure to record the molarity (M1) and initial volume(V1).

2. Record the weight of the antacid tablet. Place the tablet in a 250 mL Erlenmeyer flask.

3. Add distilled water to make sure the tablet dissolves completely.

4. Add 3 drops of the Phen (Phenolphthalein) indicator.

5. Add the HCL to the magnesium bicarbonate and phen until the solution changes color. Record the volume of the HCL in the buret. Calculate the molarity of the magnesium bicarbonate tablet. Easy squeezy!

If you have any other questions on titration, visit http://chemwiki.ucdavis.edu/Analytical_Chemistry/Quantitative_Analysis/Titration for more help!

Example of the set up of the lab. Found at http://chemwiki.ucdavis.edu/@api/deki/files/462/new_burette.jpg

Another example of how the lab could be set up. http://obelkobusnel.files.wordpress.com/2012/03/titration-equipment.gif

Sources: Class experiment, http://chemwiki.ucdavis.edu/Analytical_Chemistry/Quantitative_Analysis/Titration

 

 

 

 

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