Spectrophotometry and Beer's Law

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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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Опубликовано:

4 сен 2019

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Комментарии : 161

@olivxa_aa 4 года назад

my first time seeing prof dave without long hair and my whole world has just changed

@nessieglymps1283 2 года назад

Hahahahhahaha

@sithminimasha 2 года назад

Yes 😀

@TasTheWatcher 4 года назад

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

@Thaumius 4 года назад

*Beer Lambert Law*

@willm3027 4 года назад

Me too

@rauter828 3 года назад

@Mekhi Taylor Any method for FB hacking..

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@rauter828 3 года назад

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

@CoastalBachelor2009 4 года назад

I'm Scott Beer and I approve this message.

@jqyhlmnp 4 года назад

Hi Scoot Beer. My name is not Scott Beer.

@Bakedbaconscookedcookies Год назад

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

@TRI3NERGY 8 месяцев назад

@@Bakedbaconscookedcookieshi dark balls , i am niggativity

@nazirahmadahmad6555 3 месяца назад

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

@LittleWaffle 4 года назад

Thank you for this well-explained video !

@Gafa996Gaddisa 4 года назад

Hi professor. I always learn something from your channel.

@rebornmmmmuch 2 года назад

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

@tommysteinbrecher 4 года назад

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

@antoniocurcino9976 4 года назад

Thank you so much for the explanation!

@brianbaas8650 4 года назад

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

@sunflora27 2 года назад

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

@joshmemarrynagdey1639 11 месяцев назад

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

@evelynvarsovia3380 Год назад

Very clear explanation. thanks prof Dave

@divyanshugogna6152 4 года назад

thanks professor dave really helpful

@ahmedmadhy842 3 года назад

One of the best channels in the field

@funnyseasonalnews8193 2 года назад

Thank you professor Dave I have got relevant notes

@barbiesnack 4 года назад

I love being able to understand something!

@mermerrrrrrrrr 4 года назад

Thanks for your helpful videos

@aniawo5119 4 года назад

Very useful. Thank you.

@samhagan1520 4 года назад

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

@dumitru-claudiusergentu6720 4 месяца назад

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.

@rahilsiddique6950 3 года назад

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

@slow_bike_show 2 года назад

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

@alexting827 Год назад

@@slow_bike_show :O??

@nickelpence 4 года назад

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

@ellavaldivia6757 8 месяцев назад

Thank you professor David for this video.

@yolo_earth 2 месяца назад

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 4 года назад

Literally perfect timing!

@quintonwilson8565 4 года назад

Great vid, wish I saw this earlier.

@rosapizana8597 2 года назад

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.

@jimpanse1638 3 года назад

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?

@jagrutipaneliya4548 2 года назад

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

@mansurie 3 года назад

helped a lot thanks!

@defneurfaloglu855 4 года назад

u saved my life, thank you

@douniaelba4603 4 года назад

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

@namithacd5650 2 года назад

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

@gria8329 2 года назад

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

@ayeshariaz8380 2 года назад

Is the value of incident light always taken as 1?

@sithminimasha 2 года назад

Thank u professor Dave💗

@pritykarmakar4937 2 года назад

Thank you so much sir🙏

@tnjoegaming2458 8 месяцев назад

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

@TheEmperorjun 2 года назад

Thanks a lot professor...

@lilyanahasan8589 2 года назад

thank you for this!

@AnyanwuPeterIkechukwu-nw4ri 9 месяцев назад

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

@williamadams137 4 года назад

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

@ProfessorDaveExplains 4 года назад

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

@yunus-ff2mw 3 года назад

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

@christophernayar6543 2 года назад

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 11 месяцев назад

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 🤔

@woomp2004 10 месяцев назад

I thank you from the bottom of my heart

@hn-uv3vl Год назад

i love you so much istg thank u 🥺 for ur content ❤️

@organicnky7448 3 года назад

My favorite on internet 💎

@thomone23 Год назад

Thx 4 U'r effort ♥️

@guttipavan9306 4 года назад

easy understand. tq sir

@vicentesayson2990 4 года назад

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

@ProfessorDaveExplains 4 года назад

seems like an arbitrarily limitation to me

@vicentesayson2990 4 года назад

@@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. Год назад

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

@laibakhan8380 Год назад

Proffessor Dave, I love you.

@sivasankar3349 10 месяцев назад

how 0.35 came for molar absorptivity?

@jerryhymytang8859 2 года назад

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 2 года назад

I also thought the same

@GameHero531 2 года назад

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 Год назад

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

@GameHero531 Год назад

@@CMThota correct

@autonews1621 Год назад

thanks bro, so annoying

@user-oi1pv4jp2e 3 года назад

Thank you so much 💓 💗

@axediepied6993 3 года назад

THANK YOU!!!

@salmaalmunayes4251 4 года назад

What was it about bonding? It wasn’t explained

@scigrl2870 4 года назад

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 4 года назад

e^x is a notation for 10 to a power

@johncavanaugh3960 4 года назад

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

@kamilewais-orozco9971 4 года назад

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

@krellemaster 2 года назад

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. Год назад

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

@cliffordwilliams9597 4 года назад

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 3 года назад

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)

@sammyapsel1443 Год назад

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 Год назад

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

@bbnnationoriginal2722 8 месяцев назад

Bro just causally saved my chem grade

@user-hp7cb8if7k Год назад

Thank you from Algeria 💚🇩🇿

@user-jm5hw8mb1e 4 года назад

This relate with physics or biology???

@TommyZommy 4 года назад

Dave, are you considering making computer science lectures?

@ProfessorDaveExplains 4 года назад

yes definitely one day!

@leenalsader8476 2 года назад

Thanks 🌸

@daviskimani1890 Год назад

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

@setsu2221 11 месяцев назад

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

@adduct99 3 года назад

How is the path length selected?

@ProfessorDaveExplains 3 года назад

it's the length of the cuvet

@bennettegaper4344 4 месяца назад

Thank you

@karhukivi 11 месяцев назад

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 9 месяцев назад

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 9 месяцев назад

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

@karhukivi 9 месяцев назад

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.

@yarlankini2170 Месяц назад

Awesome 👍

@Zach-xm5wc 4 года назад

Anyone else have a broken Spec 20 for lab?

@tuna3875 3 года назад

I just realized how Professor Dave looks like moistcritikal

@fabioverdi6291 3 года назад

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.