Title- How close is Klos?

                                                        By Nick Lallas and Matt Tainter

Purpose- To figure out the molarity of an unknown acid by titration.

Procedure- As always, the materials list comes first. To begin this experiment, you will need: 1 ring stand, 1 burette clamp, 3 Erlenmeyer flasks (or Florence flasks), several strips parafilm, NaOH, H₂O, potassium acid phthalate (unknown acid), funnel, graduated cylinder, and safety goggles. Once all of the equipment is assembled and thoroughly cleaned you are ready to begin the lab.

The first process is to make your acid and base solution. To make the base solution, measure out 250ml of H₂O in a graduated cylinder and weigh out 1g of NaOH (sodium hydroxide). This will give you a .1 molar solution. To figure out the molarity of the base, simply multiply divide the number of grams you weighed out by the molecular weight of the base. Then multiply that number by the factor in which it takes to make a liter of the solution. For example, if you had 250ml of base, it would take 4 times that to make a liter of it. The simple formula for this is: M_B = g_B/molar mass x factor. We used 1g of base; therefore our molarity is .1 molar. Now you must also make up an unknown acid solution. To make the solution, measure out 200ml of H2O in a graduated cylinder and pour it into a flask of your choice. Next, add to the water somewhere between 1 and 2g unknown acid (potassium acid phthalate).

Once both the acid and base solutions are made, pour each into a separate burette. Take the volumetric reading of both burettes by correctly reading the meniscus. You can read to the nearest hundredth of a ml. Next, empty out approximately 10ml of acid into one of the flasks, and put two drops phenolphthalein into the flask along with the acid. Now the real fun begins (yeah right). Position the flask containing the acid underneath the burette containing the base. Make sure that the end of the burette is inside the flask and contains no air bubbles. The first trial that is done is simply a waste to get a rough idea of how much base it will take to make the acid change color. As soon as you have a good idea of where the endpoint is, point at which the acid turns the faintest pink in color, you can be more careful in your trials. To accomplish the task of reaching the endpoint and not making it look like Starkey's hair, you must add the base drop by drop, sometimes even hanging half or 3/4 of a drop and then washing it down with the distilled water.

  Starkey's new hair color.  Called:  Beyond the endpoint

When you have successfully reached the endpoint, or what you think is the endpoint, take the volume readings of both the base and acid. Subtract the final volume readings from the initial ones to get the amount used. Now you must figure out the molarity of the acid. Exciting.

The formula used is: M_A = M_B x V_B / V_A

An example would be: MA = .1 x 3.32 / 12.73  = .026

*These trials were thrown out. We decided to eliminate the high and the low trial and average the remaining three to get our final answer of .026704535 which, comes out to be a ?? % error.  (This was calculated by my dad, the Chemistry teacher.  In order to do this you have to know the molecular weight of the unknown acid so you can calculate its molarity.)

Matt watching Nick do the calculations

Observations- Many things could go terribly wrong with this experiment if you are not overly careful in your actions. If there are bubbles in the burette tips, your readings could be thrown off. Not reading the meniscus correctly will easily give you a false answer. Not rinsing out your burettes and titration flasks out with acid or base before using them will also mess up your answer. Incorrectly judging where the Starkeypoint is will also mess you up as will letting Mr. Lallas titrate for you. The more trials that we did, the more accurate or more consistent our figures were, however, it became more and more crucial to correctly read the meniscus to determine our final volume readings. Another important factor is to go around and ask other people what they are getting for readings.

If they are somewhat close to what you have, you know that you are in the right ballpark. When doing, this, you have to figure in the amount of acid they weighed out, along with the amount you weighed out. That will cause the molarity difference to be greater or smaller depending on mass.

Conclusion- This experiment not only takes a bit of skill mastery, but also requires and educated guess in the end. Once all of your trials are taken and you have several molarity readings, it is time to arrive at a final answer. This was perhaps the toughest part of the experiment, tougher than hanging 1/3 of a drop, tougher than having enough patients to obtain the faintest pink for an endpoint, tougher than...I'm running out of things to say. We decided to throw out the high and low trials and average what's left. If we would have taken our lowest reading and used that as our observed value, we would have had a much lower percent error. Three to be exact, but instead, we took the safe way out and used averages.

Perhaps the most that Matt and I got out of this experiment was being able to trust one another. Our faith was put onto each person when a volume reading was asked, or when we needed to mass out the base or acid. Either one of us could have ruined the experiment by simply misreading the meniscus once.

Last year in Chem. 1&2, acid base titration was merely touched upon. We spent 3 days learning how to be expert titrationists.  This year, over 2 weeks was spent titrating. Our techniques vastly improved from the first time we began to titrate. Not only did our physical techniques improve, but also the mental things like remembering to rinse the titrating flask out with distilled water and then rinsing it a little with acid to get the water out. Many people however, did not get such great percent errors. The lowest in the class was 3%. Next was 8% and then our ??%. These readings could very well have been thrown off by the slightest miscalculation. Something all of us encounter.

Nick after losing tip of his tongue in the spectrophotometer.