IB Chemistry Topic 11.1 Uncertainties and errors

[@AndrewWeng]

For the full video set please subscribe at: www.mrwengibchemistry.com

[@adrixx3713]

Thank you so much!! You explained everything very clearly and got straight to the point. Awesome stuff!!!

[@AndrewWeng]

Thanks for the feedback adrixx

[@vincenzorosariolafrancapit3538]

There is a mistake at 16:13 min. In your raw data the uncertainty of the beaker is 0.01 and when you shaw the calculation is 0.1

[@mmll1555]

7:35 how is the answer 4.50 shloudnt it be 4.55+\- 0.05 ? Because it’s between 4.5 and 4.6

[@AndrewWeng]

That answer is also acceptable. Any answer in the range of 4.50 to 4.60 (including 4.55) is acceptable - just that the MCQ only had one of those.

[@tanisha8322]

@@AndrewWeng Hi. Then in that case, wouldn't option 2) be correct? As 4.54 is closer to 4.55?

[@kitty7492]

I should have watched this before submitting my IA

[@lauraward6443]

so why do we use propagation uncertainty error = sqt (delta 1^2 +delta^2) and when do we use just add delta 1 +delta2 Thanks

[@jada-virginiasurpin3851]

Hello Mr. Weng. I love your videos! Anyway, enough fandomming. I have a question: I need to calculate the percentage uncertainty of my Rf values in TLC analysis. My glass micropipette has an uncertainty of 0.6µl and my ruler used to measured distances travelled by solvent and solute has uncertainty of 0.5mm. Do I add together the two uncertainties to calculate % uncertainty of my data or do the calculation twice with each piece of equipment?

[@AndrewWeng]

You definitely need to use both solvent and solute movement in cm in your uncertainty calculations. As far as the pipette is concerned, it might be a nice IA to determine if the size of the sample affects Rf. Otherwise ignore it as it is not strictly to do with the measurement.

[@invalidusername1239]

17:37 when you divide or multiply we shoudl have the fewest significant figures, the answer should be 0.983 +/- 0.06

[@AndrewWeng]

Hi Bryan, when working out the final number of number of sig figs, you cant state your answer as more accurate than your uncertainty. So you need to state the answer as 0.98 not 0.983.

[@zytpxx5311]

u did ur whole thing wrong bro because u misread .01 as .1 for the mass of beaker

[@AndrewWeng]

Need a time stamp. Do you mean 16.02?

[@slimshady1394]

Hope i won't fail IB- m21 kid😂 U guys can check up on me next year and ask how i finished the IB...

[@leenalhassawi6330]

I’m in the same boat, hopefully things work out for us!

[@leenalhassawi6330]

I’m in the same boat, hopefully things work out for us!

[@urmom8565]

heyy its been one year how did you finish IB

[@slimshady1394]

@@urmom8565 41/45 :)

[@nicoleguajardo1220]

@@slimshady1394 I’m so happy for you, I’m a junior and in IB. Im thinking of creating perfume for my AI. However I don’t know if I can use that for my AI I have to ask my teacher. So if any one is reading this I hope you can give me guidance and how I can apply this.

[@loiubh]

What about mass change? Suppose I have an initial mass 0f 128.56 +- 0.01 and the final is 128.58 +- 0.01. Does that mean that my %uncertainty is 100%???

[@AndrewWeng]

Hi Joao, I have to know exactly what you are doing with these two numbers. If you are taking away final mass from initial mass, then yes 0.02 +/- 0.02. In this case you have a clear method error as nothing is happening or at least you should be using an analytical balance that measures +/- 0.0001

[@williamcullen2759]

Do you know how to work out the uncertainties for an arrhenius equation. Applying ln to k and 1/temperature? I can't find it anywhere. Hope you can help!

[@AndrewWeng]

Email me your calculations.

[@asuramaru291]

17:10 why did we multiply the values for the last time?

[@atarchem]

Hi Sina, we are simply converting back from a percentage to an absolute value.

[@invalidusername1239]

17:37 again, you asked us to multiply the uncertainty by 100%, but then you have this 0.9833+/- 5.9887% ------>> 0.059887 x 0.9833 no percentage?.

[@AndrewWeng]

Yeah I am doing some skipping steps writing and not writing 100%. Let me know if you think there is an error though.

[@shreyajolly6763]

what would be the final uncertainty when combing values having different parameters for measurement Say 1.00 g (±0.01g) + 23.5 (±0.05 cc) ??? also does every uncertainty of the final calculated value have to be expressed to one significant figure

[@AndrewWeng]

Yes all final calculated values of uncertainty are only ever one sig fig. As for the adding, you need to covert cc to g. Assume they are the same but state this.

[@maggiesun5423]

In example 1, why the wooden stick is not 4.54+- 0.05 cm?

[@AndrewWeng]

Measurements must be taken in 0.05 increments, not 0.01 increments - they must match the uncertainty. 4.50 or 4.55 are acceptable readings.

[@maggiesun5423]

@@AndrewWeng Thank you so much for clarifying!

[@KelanProductions]

Systemic or systematic?

[@AndrewWeng]

systematic. no doubt I said systemic somewhere right?

[@rashedrashed6687]

9:12 how did we know that 9 is the average I still don't get it !!!!

[@harshithadavanam1688]

yo does anyone have notes for hl chem year 1 pls send😭😭😭😭😭

[@nalaking1072]

since u graduated DO U HAGE ANY NOTESSSS please send

[@pablovalle81]

you are god