Random and Systematic Errors in Titrations

[@susan3883]

Anyone pause the video and grab an ice-coffee out of the fridge before continuing on withe the video. This video was extremely helpful and esp. since I was working on a Titration report at the time.

[@billstapleton2071]

Susan this is deadset the best comment I have ever had. Made me laugh, thanks heaps! Glad it helped

[@susan3883]

@@billstapleton2071 Thanks so much for reading the comment. I am glad you liked it. I actually did get an ice-coffee before I continued with the video as there was one in my fridge so....

[@billstapleton2071]

Sorry about the audio quality, this was one of my earlier videos!

[@lauratew]

Hello Bill! Just came across your nice vid here so I've subscribed. Laura from SVCC!

[@billstapleton2071]

Thanks! Great to hear from you! Hope you are doing well

[@lionelpickford9243]

You are such a legend Mr. Stapleton!

[@robot5254]

If I fail my chem practical I’m coming for u

[@billstapleton2071]

Max Ahmed how’d you go? Do I need to move? Hope the video helped!

[@robot5254]

Bill Stapleton helped me finally understand the difference between systematic and random error the practical exam went great

[@jasperbutcher2596]

Helpful, nice handwriting too

[@reeseyvuitton4257]

Higher titre equals higher concentration value? Or lower concentration value? It's been changing in the video

[@nethmiw5783]

The video was very helpful! Thanks alot!

[@ntodrizzy6597]

I didn’t understand the bit of not filling the below tap what do you mean. We should fill solution till below the tap.

[@billstapleton2071]

Hi Drizzy, if you do not fill below the tap then it is a random error as the titre value will appear higher than it should be. You are correct in that to perform a titration correctly, you must fill below the two before your first titration

[@ntodrizzy6597]

Thanks dude can you tell me few errors like systematic, human and random for a titration for KHP Vs NaOH please. Also how I could reduce them as well the errors.

[@ayaalammo3709]

great video, thanks a lot.

[@bellaihaia7860]

Thanks Bill, this really helped. Youre great man :)

[@1babyborn]

is rinsing the burette systematic or random error?

[@billstapleton2071]

Hi Naomi. If you don't rinse the burette, it will be a random error. It will affect your first one or two titrations, but once you have to refill the burette it will pretty much disappear and will no longer affect your results. Hope this helps!

[@1babyborn]

@@billstapleton2071 thank you

[@musaratshah9860]

Video helped a lot thanks

[@benshore9407]

Love the FU Icec cofee sponsorship!

[@billstapleton2071]

Lol thanks Ben. Couldn't stay awake at night to make the videos without it!

[@fernsqurrel]

Thank you very much great video sir!! :)

[@qaharjuwon2004]

Thanks

[@zl1710]

really helpful thank you

[@fsfs547]

Hello sir, how does the concentration increase when the titre is low in 6.07

[@kirtanpatel1381]

He has actually made quite a lot of mistakes, including the one at 6:07. Suppose, 10 ml of the titre is actually added to the reaction vessel, but the added drops from the funnel reduce this to a measured reading of 5 ml, which will be used in calculations. Since, less moles of the titrant will be calculated to have had entered the conical flask and reacted, less moles of the titrand will be present in the same volume as per the calculations so the calculated concentration would be lower than the actual concentration. The one at 6:07 is actually a systematic error, since the error would have a unidirectional effect on the concentration calculated (always results in a lower concentration), but the extent to which its lower varies as the number of drops that drop into the burette from the funnel. At 8:40, consistently rinsing the pipette with the wrong solution will be a systematic error, rather than a random error as it changes the final calculated concentration in one direction only (either it always gives a lower or higher titre volume than the actual amount throughout the many titration trials, depending on whether the acid or base was used for rinsing). Inaccurate and imprecise results will be produced (rinsed to a different extent each time, thus affecting concentration differently each time). At 10:24, the bubble at the bottom end in the pipette and the burette is actually for calibrating the glassware and not an error, but rather it improves the accuracy of the measurement. Once the bubble is removed from the outflow of the titrant, it will return again once the stopcock is turned off so it will not affect the initial and final reading of the titrant.

[@kirtanpatel1381]

The one at 6:07 is actually a systematic error, since the error would have a unidirectional effect on the concentration calculated (always results in a lower concentration), but the extent to which its lower varies as the number of drops that drop into the burette from the funnel.

[@billstapleton2071]

@@kirtanpatel1381 Hi Kirtan, to clarify some of your comments: 1. With regards to the calculation, if your unknown concentration is in the burette, then a lower titre value against your known standard solution in the conical flask will result in a higher calculated concentration for the unknown sample. Example: If HCl is in the burette and is titrated against 0.105M Na2CO3, a titre value of 24.35mL would give you [HCl] = 0.1725 M, but a titre value of 22.35 mL (due to drops from the funnel moving the meniscus back higher) would give a [HCl] = 0.187 M. This is because the extra drops make it appear that there are more moles in a smaller volume, hence increased final concentration value. This video is designed for my high school students where we always have our known solution in the conical flask, so apologies if this has caused confusion. If the funnel is only left in for one of the titrations, then it will be a random error. This is what I was trying to explain. Even if it was left in every time and the number of drops changed each time as you indicate, this is again not a consistent error, so it will still be random. Yes it will result in a lower concentration each time, but not always by the same amount (which is what a systematic error would result in). 2. I agree, if you consistently rinse the pipette with the wrong solution it will be systematic, but students are taught to only rinse with the solution being used the first time. There is no need to rinse again after that, so any of the initial wrong solution that was used would have gone with the first titration, hence why it is a random error as it only would affect the first titre value. 3. I am referring to air bubbles that may be present due to sucking up air when filling the pipette. These take up space in the pipette and mean that the volume is less than the stated value on the pipette. Sorry if this was not clear.

[@jakehaagman7574]

rp