Yes, the Henderson-Hasselbalch equation gives only an approximation due to the assumptions made in deriving it. This is why the best practice is to use a meter to check the actual pH and use acid or base to adjust the pH before making the final dilution.

Nevermind, I was thinking the conjugate acid was HCl instead of TrisHCl. So it makes sense, since there is still some Tris left, besides the amount that reacted with HCl to form Tris-HCl, hence n(Tris) + n(TrisHCl) = total amount of moles in the buffer. Just leaving this here in case anyone has the same problem. Thank you for the video!

but shouldn't 50mM be the concentration for Tris-Hcl only, and not Tris-HCl +Tris?

@@jpedroam1692 By definition, the concentration of a buffer is the *total moles of buffer* (conjugate acid + conjugate base) per liter. There are three ways to make a buffer. Since you need to add enough Tris acid and/or Tris base to equal the total number of moles, you can add (1) all acid form, (2) all base form, or (3) some of each. It is often easiest to just add one form and then use either a strong acid or base to adjust the pH to the desired value. I show all three methods in this video.

@@MichaelGaroutte alright, got it. I thought the concentration refered only to Tris-HCl and not Tris. Thanks again!

Glad that it helped!

The pKa values of some buffers change with temperature more than others. I found this link to a PDF that lists correction factors (dpKa/dT) for many buffers. www.itwreagents.com/download_file/info_point/IP-022/en/IP-022_en.pdf

@@MichaelGaroutte thank you so much Sir

You need to add enough Tris acid and/or Tris base to equal the total moles of buffer required. You can add all acid form, all base form, or some of each. It is often easiest to just add one form and then use a strong acid or base to adjust the pH to the desired value. I show all three methods in this video.

I am afraid that I do not understand your question. Could you please clarify?

Hello, Alejandra! Please check to see if the other comments on the video answer your question. 😊

You have to do the *inverse* log (antilog) of -0.57. This is likely a button labeled 10^x on your calculator.

@@MichaelGaroutte thank you so much for your help

the 1 added to the 0.269 was from the CA

in math, for example x +x = 2x, same with the 1 of CA present in the solution

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@@jomarienarag435 Perfect explanation. Thanks!

Good question! We use a buffer to keep the pH constant, often when studying a biochemical reaction. We need enough buffer capacity to neutralize any added acid or base, for example, if the reaction generates protons (acid). In other words, the concentrations of the reactants should be much less than the concentration of the buffer species. Since most biochemical reactions with enzymes use concentrations of 1mM or less, a 50 mM or 100 mM buffer is usually sufficient. We don't want to add more ions than necessary, both because there is no need, and also to avoid the ionic strength changing the reaction we are studying, so we don't want to use higher concentrations of buffer than necessary (say, 1 M).

Good question! Technically, yes - but since the equation uses a ratio of CB/CA, if CB is in mol/L, and CA is in mol/L - and they are in the same solution - the liters are the same for both and cancel out. So you can just use moles. :)

I'm afraid I do not understand your question. You can use the phone to share your writing for as long as you like during the Zoom call.

Join with meeting ID. You have a personal meeting ID in your Zoom settings. The meeting ID is also shown at the top of the Zoom window on your PC after you start the meeting.

@@MichaelGaroutte Hi Michael, I got into the meeting with my phone but now I cannot seem to display what the iphone video is showing. I clicked on screen in the phone and it shows screen broadcast (first line), Zoom (second line) and start broadcast (third line). If I click on start broadcast I can see the phone display on my laptop but I cannot leave the zoom app and go to the camera to video the paper to write on. Sorry to be so slow, but I just haven't done anything like this. Thanks for any help.

@@MichaelGaroutte I can see my connection as a participant on my laptop and I can raise and lower my hand. There is a ringing echo with any noise that is annoying. Finally, it sucked down my battery really fast. I went from 100% to about 12% in just a few minutes, so I plugged it back in to the charger. I don't know if any of this means anything. I'm just trying to give you the situation as I see it. Thanks again for any help.

@@philbeauchamp2884 It sounds as if you may be doing a Zoom web conference and not a Zoom meeting. Also, you need to join on your phone *without audio* to avoid the echo. The steps would be, 1) Create your Zoom account. 2) Click "My Account." You should see your Personal Meeting ID. Write it down. 3) On your computer, hover over "Host a Meeting" and choose "With video on." 4) Open the Zoom app on your phone, and click "Join." 5) In the Join options, choose "Don't Connect to Audio." (Note: I have an Android, so the iPhone app may look different. I don't have access to that to check.) 6) Enter the meeting ID that you wrote down previously. You will join the meeting. In my case, it defaults to the front-facing screen. But there is a little Camera icon on the screen to change to the back-facing camera. 7) Prop the phone in a good location and you're set!

I'm glad it helped!

Because you will convert 0.010 mol of glycine to the conjugate base form using hydroxide. I explain this in the video from about 3:00-4:30.

AHA! I get it now! Thank you.