Titration Video

welcome to the UNL chemistry department in today's

video

we will see the proper technique and procedure for

titration

s let's get started this is what you will need a bottle of KHP a weibo poured the KHP powder a spatula some deionized water make sure not use tap water, its concentration of NaOH phenolphthalein unknown. I think you are already familiar with this indicator. A retina burette of beer, sand and several measuring cups, dissolve your khv and collect the waste and of course at any time. When working with chemicals, you must wear gloves and safety glasses. I recommend cleaning your burette first because you have no idea who last used it or what was in it.

To do this, you will need to wash it with deionized water in the Typically, you would do this two or three times to make sure that the burette does not have any impurities inside. We use deionized water to clean to prevent tap water chemicals from contaminating our burette and throwing off bid calculations later, the next thing to put in. your burette on the stand using your unknown NaOH solution rinse the inside of the burette while you do this you should try to get any bubbles out that may be in the tip of your burette. Bubbles will alter the accuracy of your

titration

for more details on how to properly rinse your burette in preparation for a titration watch the burette technique

video

linked in the description below once it is completely rinsed you can top off your burette with your ramp tight and then you will need to zero your burette to get ready for your titrations.

Remember that your initial reading does not have to be zero, but will need to be documented for your future calculations. Now we are ready to find the mass of our K HP. k HP stands for potassium hydrogen phthalate and will react with NaOH in a molar ratio of 1 to 1. Write down the formula weight of K HP here on the bottle. You will also need this mass for your calculations. I'm sure most of you have used a scale before, but remember to zero the arc before weighing your K. HP here I'm aiming for 300 milligrams of K H P but getting exactly 0.3 grams doesn't matter much as long as it's close, This may take a while to get closer to my desired mass.

Any excess KHP should not be put back into the bottle but discard it properly ask your TA for specific instructions if you are using this style of scale be sure to slide the door closed to obtain your final mass you will need to document your KHP masses each time take one I recommend that you weigh four. separate KHP pots for your assessments, but it's really up to you how many you should do. Make sure the balance is clean. When you are done, you will need to transfer your KHP to a class that contains approximately 100 milliliters of water, the exact amount. of water doesn't make a difference, but the exact mass of khp does remember this is deionized water, not regular tap water, rinse your waves three or four times with deionized water to make sure all your K HP is transferred.

This technique is called Quantitative Transfer. Another technique you could use is called mass difference. See the description below for a link to the balanced video of this technique. KHP may take a while to dissolve, but it is important to ensure that it is completely dissolved before beginning titrations. Here what I am doing for the titrations, the first one is known as a Scout titration, more on this in a moment, then add a few drops of phenolphthalein, two or three drops per flask will be enough now that we are completely ready to start our titrations, ask If the titration is Completely Optional, this titration is usually done fairly quickly and does not need to be very precise.

The goal of an exploratory titration is to get a rough estimate of how much titrant you will need to add to the rest of your solutions. Titration will only be valuable if the KHP masses are close to each other. The masses do not have to be equal, but they must be within 25 milligrams of each other. Here my Scout qualification tells me that I need approximately fifteen and a half milliliters of NaOH for each of my solutions, now we can start with our more precise assessments. My Scout rating allows me to lower the buret to 13 milliliters before I have to start adding more slowly and eventually drop by drop until I see a color change that I need to taper off. drop two to two and a half milliliters before the point indicated by your Scout qualification.

This is because during Scout titration it is very easy to over titrate without knowing that this process can take a while, but in order not to go past your equivalence point you need to take your time adding your titrant drop by drop and stirring intermittently will ensure the best results by adding a white sheet of paper under the flask can help you see the color change if the black background of the ring holder makes it difficult for you to see a pale flask. Pink is the color you are looking for. You will also need to evaluate the rest of the solutions.

I will speed up the process so it doesn't take so long. Remember to get good results. This process takes some time. Do not forget. To document the initial and final burette readings, the burette I was using had markings for every tenth of a milliliter, we can tell if our volume falls between these markings, so we need to document our volumes to the nearest hundredths position. This is the appropriate number of significant values. figures for this piece of crystal here is a sample data set if you want to try a calculation on your own, stop the video at this point if you want to try it and I will post an answer here in a few seconds here is your average with the correct number of figures significant here's an extra tip for you when making your assessments to help make your results even more accurate.

You can add half a drop of titrant using your burette by simply turning the stopcock slightly to let half a drop of titrant swell at the tip by touching the side of your transfer container and swirling the solution. You will have added half a drop of titrant. Good luck in the lab.