[Music] hi I'm Jared Hyman an assistant professor of chemistry at Elon University today we will be discussing the proper titration technique using the complete single burette assembly kit available from Carolina's biological supply company this is the first in a two-part video series on titration the purpose of a titration is to quantitatively determine the concentration of an unknown solution commonly called the titrant or analyte by adding a volume of a chemical with a known concentration called the titrant to mark the endpoint of a titration an indicator is added to the analyte let's review some of the equipment that's needed for a titration carolina's complete burette assembly contains the basic equipment to get you started including a burette ring stand and a burette clamp a burette is a long narrow graduated tube used to add titrant it has a stopcock to regulate the flow of liquid notice that the markings on the burette go from lowest at the top to highest at the bottom the ring stand and burette clamp are used to mount and secure your burette other materials you will also need include a small funnel to help you fill the burette a 125 milliliter Erlenmeyer flask which works best for titrations the shape of the flask allows for more vigorous swirling than a beaker or other glassware and minimizes spill hazards a volumetric pipette and pipette bulb to transfer a known volume of analyte to the flask a wash bottle filled with deionized water a beaker or flask of titrant and of analyte indicators selected for your reaction a reading card to help read the meniscus and a sheet of white paper to help visualize the endpoint to prepare your burette for the titration it is good laboratory practice to rinse your burette thoroughly with deionized water then with a small amount of titrant after each rinse open the stopcock to allow the liquid to drain at the bottom if there is a lot of liquid clinging to the walls of the burette then thoroughly clean your burette and the rinse process the accuracy of this technique is dependent on the titrant flowing into the flask and not sticking to the walls of the burette mount burette in the clamp making sure it is positioned vertically and there is enough room to position your flask underneath the tip check to see that the stopcock is in the close position insert the funnel into the top of the burette and fill with titrant almost to the top filling exactly to the zero mark is not necessary but you do need sufficient titrant to complete the reaction check the column for air bubbles and gently tap to free them from the sidewalls remove the funnel place the Erlenmeyer flask under the tip and open the stopcock to allow a few milliliters of titrant to flow through releasing any trapped air rinse the tip of the burette with water empty the liquid into a waste container and thoroughly rinse the flask it is not necessary to dry the flask record your starting volume it is important to accurately read the volume on the burette first note that the liquid forms a concave meniscus because the water pulls itself up the sidewalls of the glass you should read the volume from the bottom of the meniscus at eye level secondly it is important to read your volume to the correct number of significant figures this burette indicates volume to the nearest point 1 milliliters with any graduated glassware record the volume to one additional decimal place beyond the smallest graduation in this case record the volume to the nearest hundredth of a milliliter estimating the final place use the volumetric pipette to transfer the analyte to the flask add a few drops of indicator to the flask and swirl place the flask under the tip of the burette record this volume placing a piece of white paper under the Erlenmeyer flask may make it easier to detect the color change operating the burette requires two hands one hand turns the stopcock while the other hand swirls the flask practice turning the stopcock a few times to familiarize yourself with how quickly the flow starts and stops it is common laboratory practice that the first titration is an estimate open up the stopcock and allow the titrant to enter the flask quickly continuously swirl the flask as the volume of titrant in the flask increases the color of the indicator appears then disappears as you swirl when the analyte becomes a colored solution close the stopcock record the final volume of the burette subtract the initial volume from this final volume to get the estimated volume of titrant needed for this titration knowing the volume that is a little past the endpoint subtract 5 milliliters from that number to get the amount of titrant that can be safely added before a slower addition is required as the estimate titration shows a dark colored solution indicates an excess of titrant has been added the desired endpoint is a pale faintly colored analyte to reduce the risk of passing the endpoint slow down the addition of titrant when flashes of color begin to appear in the analyte adjust the stopcock to slow the flow of titrant to a drop-wise rate continue to swirl the flask with one hand and keep the other hand ready to close the stopcock when you notice the indicator taking longer to fade close the stopcock rinse the tip of the burette with deionized water and swirl the flask record the final volume on the burette if the analyte remains faintly colored then you have reached the end point if the analyte is still colorless then repeat these steps add a drop rinse swirl and record until a faint color persists typically titrations are performed in triplicate use the average volume of the titrant required to reach the end point for any calculations you now know how to properly perform a titration be sure to check out the second video in this series in that video we will go over the proper procedure for determining the concentration of an unknown acid solution using a base of known concentration Carolina has everything you need 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