Spectrophotometry and Beer's Law

We've learned about kinetics already, but how do we gather kinetic data? One clever method is by analyzing how the color of a solution changes over time, which is an indication of the concentration of certain compounds that interact with light in a specific way. This technique is called spectrophotometry, and this type of analysis will involve calculations using Beer's Law. Let's take a closer look!
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my first time seeing prof dave without long hair and my whole world has just changed

[@nessieglymps1283]

Hahahahhahaha

[@sithminimasha]

Yes 😀

[@TasTheWatcher]

Beer's law? Aye, I'll drink to that.

[@Thaumius]

*Beer Lambert Law*

[@willm3027]

Me too

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[@rauter828]

@@masterally6025 I understood..I never tried..just to know what will be d reply..

[@CoastalBachelor2009]

I'm Scott Beer and I approve this message.

[@jqyhlmnp]

Hi Scoot Beer. My name is not Scott Beer.

[@Bakedbaconscookedcookies]

​@@jqyhlmnp Hi not Scott Beer..... I'm Dark balls

[@TRI3NERGY]

​@@Bakedbaconscookedcookieshi dark balls , i am niggativity

[@nazirahmadahmad6555]

I can't explain how to thank you .Tomorrow is my test and now I'm feeling relax.

[@sunflora27]

thanks professor dave! This helped reiterate what my online course just blew through rather quickly

[@tommysteinbrecher]

Wow I was just lectured about this in chem and now studying for the midterm in 2 days what’re the odds hell yes professor dave

[@Gafa996Gaddisa]

Hi professor. I always learn something from your channel.

[@amelielambert2337]

Thank you for this well-explained video !

[@barbiesnack]

I love being able to understand something!

[@rebornmmmmuch]

Very well explanation. Now I get the idea what this is all about🙏🏻

[@joshmemarrynagdey1639]

Thanks a lot... you make the topic easy to understand.

[@antoniocurcino9976]

Thank you so much for the explanation!

[@evelynvarsovia3380]

Very clear explanation. thanks prof Dave

[@funnyseasonalnews8193]

Thank you professor Dave I have got relevant notes

[@rahilsiddique6950]

Thanks a lot Professor Dave, you are literally a life saver

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he is he has canonically saved over 200 people from trains, mugging and chemistry mishaps. This is his penance as professor Dave caused the 2011 Fukushima Nuclear Disaster

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@@slow_bike_show :O??

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One of the best channels in the field

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Nice first like and Comment! Loving your channel Bro, I always learn something from you 👌🏻👍🏻😁😎

[@divyanshugogna6152]

thanks professor dave really helpful

[@ellavaldivia6757]

Thank you professor David for this video.

[@yolo_earth]

Thanks for your video, Professor Dave! one thing to mention, it might better to tell log used here is actually base with e, not 10. In context it explained greatly, but itself I got bit confused for secs.

[@Mt.Trashmore]

Literally perfect timing!

[@nickelpence]

Just shared the video with a friend who didn't understand wery well what they did just today at chemistry class😉

[@mermerrrrrrrrr]

Thanks for your helpful videos

[@aniawo5119]

Very useful. Thank you.

[@samhagan1520]

You are easily better than my chem lab ta. Thank you. Ps. I like the new haircut.

[@quintonwilson8565]

Great vid, wish I saw this earlier.

[@woomp2004]

I thank you from the bottom of my heart

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Thank u professor Dave💗

[@mansurie]

helped a lot thanks!

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Thanks a lot professor...

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u saved my life, thank you

[@pritykarmakar4937]

Thank you so much sir🙏

[@lilyanahasan8589]

thank you for this!

[@christophernayar6543]

For a part of my project, I was thinking about making a standard curve type thing, like make a range of dilutions and then plot the absorbance against the dilution concentration and then have the computer put a line of best fit. Then any sample I run with that substance I can just plug it into the graph. Would that give me a fairly accurate concentration? Would the concentration vs absorbance be linear? Thanks

[@setsu2221]

It depends on several factors, but perhaps most importantly whether you are below, I believe, 1 ABS. Around ABS>1, the correlation becomes nonlinear. You may also have to account for variables such as temperature change and material properties. The spectrometer i use has water cooling and a temperature controller, but I doubt most have that 🤔

[@thomone23]

Thx 4 U'r effort ♥️

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My favorite on internet 💎

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[@namithacd5650]

Can you do one for thin layer chromatography? Would be greatly helpful!

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THANK YOU!!!

[@guttipavan9306]

easy understand. tq sir

[@jagrutipaneliya4548]

Could you give me a name of software where I can plot my graph in better way?

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Bro just causally saved my chem grade

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Proffessor Dave, I love you.

[@user-oi1pv4jp2e]

Thank you so much 💓 💗

[@jerryhymytang8859]

Hi professor Dave, I realized that you convert the log with a base of 10 to a exponential with a base of e, shouldn't it be in the base of 10? or else a natural log should be used instead of log in the base of 10

[@muthegameonline]

I also thought the same

[@GameHero531]

It's unfortunate and rather annoying but some textbooks and professors use log to mean "log base e", while others use it to mean "log base 10". It makes sense to just call log base e "log" if you know where the logarithm operation originally came from, but it's confusing nonetheless

[@CMThota]

​@@GameHero531 so basically he meant log base e (ln) not log base 10? (the terminology is a bit new so just clarifying :))

[@GameHero531]

@@CMThota correct

[@autonews1621]

thanks bro, so annoying

[@tnjoegaming2458]

Sir can u pls give a lecture about calorimeter principles and its application..

[@jimpanse1638]

Why is the number of moles a concentration? Isnt the concentration moles/volume? How can i get the total number of moles in the cuvet?

[@vicentesayson2990]

Do you think sir, it's a good idea to create a spectrophotometer using specific wavelength only? For water analysis?

[@ProfessorDaveExplains]

seems like an arbitrarily limitation to me

[@vicentesayson2990]

@@ProfessorDaveExplains can you explain further? By the way sir, I conducted some experiment using pasco spectrometer, i see that at 650nm wavelength the water absorbance of a distilled water is 0 , that's why i'm thinking to use 650nm as a standard source of light to determine the impurity of water

[@Ajay-Maurya.]

@@vicentesayson2990 anything would do right? light absorved same?

[@williamadams137]

Is “log” log base ten? Because i usually see people use “Log” or “ln” for natural log.

[@ProfessorDaveExplains]

yep if the base is not specified it's implied to be 10

[@yunus-ff2mw]

@@ProfessorDaveExplains Also, in our experiments, we took the logarithmic as 10 instead of e.

[@leenalsader8476]

Thanks 🌸

[@douniaelba4603]

Hi professor Could you do a video about asanning electron microscop plz

[@bennettegaper4344]

Thank you

[@dumitru-claudiusergentu6720]

Hi Dave, since A is log (I/I0) and A is e*b*c, then I = I0 * 10^(-ebc), not I0*exp(-ebc) because it is not a natural logarithm but a base 10 logarithm.

[@rosapizana8597]

My professor used the example as an activity for the class but she asked which compound the measurement belongs to and I have no idea how to determine that.

[@AnyanwuPeterIkechukwu-nw4ri]

Please professor Dave, why do you use Iø as 1?

[@gria8329]

On the example why is the initial intensity 1, where did that 1 came from??

[@yarlankini2170]

Awesome 👍

[@scigrl2870]

Hello, thank you for your videos - I show them to my undergraduate chemistry classes on occasion. However, there is an error in this video - the opposite of log is 10^x not e^x

[@kamilewais-orozco9971]

e^x is a notation for 10 to a power

[@johncavanaugh3960]

@@kamilewais-orozco9971 Mathematically, that makes absolutely no sense. But so be it.

[@kamilewais-orozco9971]

John Cavanaugh it doesn’t, but it’s helped me sort it out in my head

[@krellemaster]

log(x) is ambiguous and can be used to represent both base e and base 10. It is exceedingly common to use it as base e in physics.

[@Ajay-Maurya.]

​@@kamilewais-orozco9971 e is a special constant appearing in nature

[@ayeshariaz8380]

Is the value of incident light always taken as 1?

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I just realized how Professor Dave looks like moistcritikal

[@eewls]

Thanks

[@ashishbhattacharya2807]

Thanks..

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You're not professor Dave...

[@ProfessorDaveExplains]

Um, yes, I am Professor Dave. The channel is called Professor Dave Explains. See?

[@gabriellanyirenda649]

It's because of the short hair isn't it😂😂

[@karhukivi]

Should that not be Ln and not Log(10) ? If A = Ln (1/0.12) = 2.12, that gives c=3.03M If you put c=3.03M into the exponential function, then the absorption is 0.12 as given in the example.

[@pablodumas9446]

It doesn't matter which logarithm base one uses (natural logarithm of base e or logarithm of base 10, the latter of which is most common for absorbance), the result will still be consistent with the formulae. Here's the logarithm of base 10 calculation step by step: 1. .9208/(.35*2)=1.3154285714285714 2. 1.3154285714285714*2*.35=0.9208 This is what's shown in the video at 4:58. From 'en.wikipedia.org/wiki/Beer%E2%80%93Lambert_law', uppercasing the important parts: '''It correlates the absorbance, MOST OFTEN EXPRESSED as the negative DECADIC logarithm of the transmittance'''.

[@karhukivi]

I'll look at that again, thanks! I also noticed that there are only 2 significant figures given in the example...

[@karhukivi]

If you go to 3:41 there are two expressions one using Log (base 10) and the other is an exponential function i.e. Ln or log to base e. If you put the values for e, b and c into the exponential function you get I/Iº = 0.3897, not 0.12 as shown later. It looks like two types of logs have been mixed up.

[@fabioverdi6291]

Help with a question ????? A compound absorb light in 227 nm. The standard curve calibration for the compound is Abs = 372x + 0,6432 which the concentration is g/100mL. The technique was analytical standard adding from fluoxetine hydrochloride (C17H18F3NO.HCl - molar mass = 345,79 g/mol). So determine the concentration in mol/L from the analysed solution. Show all calcs progression.

[@supunmalinthasandanayaka885]

Good vedio ♥️

[@ronanclark2129]

Hearing all these numbers made me anxi😢us about my homework so maybe I'll watch the rest another time

[@sammyapsel1443]

Can someone point out the following: If Transmittance is defined as I/I0, then why isn't Absorbance defined as A=1-T , but rather as A=-log(T)?

[@sammyapsel1443]

What does then 1-T signify? The percentage of light that doesn't get transmitted which is not the absorbance?

[@daviskimani1890]

Hey professor can you explain on how to calculate percentage transmittance. please😊

[@setsu2221]

Absorbance = 2 - log_10(%T) Example: 1 = 2-log_10(T) T = 10%

[@cliffordwilliams9597]

I'm confused how did we go from log I/i0, to e to the power of stuff?? Should it have been ln I/i0?????

[@12uullaass12]

I think he made a mistake he mistook log(I/i0) with ln(I/i0). it should have been I = i0* 10^-(epsilon*b*c)

[@TommyZommy]

Dave, are you considering making computer science lectures?

[@ProfessorDaveExplains]

yes definitely one day!

[@alizedan3442]

Greaaaaat

[@sivasankar3349]

how 0.35 came for molar absorptivity?

[@Negativecommentorfornonsense]

Verification of beer lambert law through colorimetric

[@Zach-xm5wc]

Anyone else have a broken Spec 20 for lab?

[@rassimsimou1594]

Good

[@chrisyun4960]

nice cut

[@adduct99]

How is the path length selected?

[@ProfessorDaveExplains]

it's the length of the cuvet

[@user-jm5hw8mb1e]

This relate with physics or biology???

[@konstantinrebrov675]

Can you teach us how to make beer from a chemist's perspective?

[@salmaalmunayes4251]

What was it about bonding? It wasn’t explained

[@Philosjutsu]

I like the look

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PROF. DAVE LANG MALAKAS (in filipino-only prof.dave is strong)

[@scott_meyer]

Beer's law? Drink it.

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Fuck you're good Prof Dave

[@abuhureyraat-tijani6113]

2:50

[@curtpiazza1688]

👍

[@FarukUmarBello-eq1zu]

Please how did our I become 1?

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Clint david sala and James Hendrick Aban Shourtout🎉

[@mactavish1411]

Anyone here to learn all of AP chem for the 2020 exam? ~We're all in this together~

[@twinklefavour2983]

I'm August beer and i approve this video

[@petranuth7112]

Beer Lambert's Law

[@hazemal-hajaya9049]

👍👍👍

[@yayapuncio497]

the more of a substance the light travels through

[@yayapuncio497]

the more of it that will be absorbed

[@yayapuncio497]

the higher the concentration the more of the substance will be absorbed

[@chickenschnitzel238]

can please someone do a remix of the intro. I am talking 24h version

[@doriankiss1]

When it says log, I guess that's the natural log, ln.

[@AR-gd6yo]

3:18 I got lost here

[@uguuuguunen9544]

kzbin.info/www/bejne/ranVcniCmr2fm80 at around 2:35 he visualizes that and it made sense

[@niharikavase3387]

It is tough 🙁

[@jmcadoesvids359]

This would have been useful 3 months ago, when i was actually seeing this shit in college