Presentation on theme: "Performing a titration A bluffers guide! Preparing a standard solution 4 Accurately weigh a weighing bottle, recording the mass 4 Add approximately x."— Presentation transcript:
Preparing a standard solution 4 Accurately weigh a weighing bottle, recording the mass 4 Add approximately x g of your substance to the bottle. 4 Re-weigh and record the mass 4 Tip the substance into a 100cm 3 beaker
4 Rinse out the weighing bottle with distilled water a couple of times. Add the washings to the beaker. (It is important all the solid goes into the beaker) 4 Pour about 25cm 3 of distilled water into the beaker (but do not exceed half-full) 4 Stir with a glass rod until all the solid has dissolved
4 Transfer the contents of the beaker into a 250cm 3 volumetric flask, carefully, using a funnel. 4 Rinse the beaker and glass rod a couple of times, adding the washings to the flask, then wash the funnel twice as well. –This technique ensures all the solid is transferred.
4 Add distilled water to the flask to about 1cm below the graduation mark 4 Using a clean pipette add distilled water until the bottom of the meniscus is just touching the graduation mark. –DO NOT EXCEED THIS MARK ON PAIN OF DEATH!!
4 Stopper the flask, with the correct sized stopper, (Hint: Check this point before starting!!) and invert several times 4 You have now made a standard solution, the molarity of which you know exactly. 4 Having done all this correctly: stop and look very smug!!
4 Use a pipette and pipette filler to withdraw 25.0cm 3 of standard solution from the volumetric flask and transfer it to a conical flask 4 Use a clean beaker to fill a burette with the solution that you are titrating with.
Good practice includes 0 Not looking up at the beaker (This can be dangerous). You should be filling it from above, ie looking down on it!! 0 Ensure the tap is closed (Please!!) 0 Use an appropriate clamp!! 0 Use a funnel to perform this procedure 0 Run a little solution into the beaker to remove any air bubbles
More ways to get an A* 0 Take the funnel out before recording the starting volume 0 It does not have to go to 0.0cm 3 0 Make sure you are aware you can record these volumes to 2dp, so therefore ensure you do record all volumes to 2dps!!! 0 Be consistent, always record to the bottom of the meniscus
Couple more things 0 Use a white tile when doing the titration 0 Add the solution from the burette in small amounts, swirling all the while
Finally 4 The end point will be an obvious sudden colour change. 4 Record the volume used and work out the volume used. This is your rough titration. 4 Do several more titrations until you achieve concordance (two readings within 0.1cm 3 ). 4 Add the solution dropwise as the end point approaches, swirling at the same time.