The removal of this proton results in NH 3 , which is easily seen at the submicroscopic level. But NH 3 is one of the compounds we know as a weak base. Another example, this time starting with a weak base, is provided by fluoride ion:. The submicroscopic representation above shows how the addition of a proton to fluoride converts a weak base F - in green into a weak acid HF. Whenever an acid donates a proton, the acid changes into a base, and whenever a base accepts a proton, an acid is formed.
An acid and a base which differ only by the presence or absence of a proton are called a conjugate acid-base pair. The use of conjugate acid-base pairs allows us to make a very simple statement about relative strengths of acids and bases. The stronger an acid, the weaker its conjugate base , and, conversely, the stronger a base, the weaker its conjugate acid.
This table enables us to see how readily a given acid will react with a given base. The reactions with most tendency to occur are between the strong acids in the top left-hand comer of the table and the strong bases in the bottom right-hand comer. If a line is drawn from acid to base for such a reaction, it will have a downhill slope.
By contrast, reactions with little or no tendency to occur between the weak acids at the bottom left and the weak bases at the top right correspond to a line from acid to base with an uphill slope. I would definitely recommend this site to my friends who think organic is boaring subject…. Once again thanks….. And when? I have heard it from one other person a few years ago.
If so, that is awesome! When trying to choose a compounds with the highest acidity, according to CARDIO, how do you determine which factor you should prioritize first? When you remove the proton the benzene ring is stabilized by resonance but the HCC- has a lot of s character in its orbital. How would you determine which compound is more acidic? Just wanted to sincerely thankyou for transforming an extremely difficult subject into something comprehensible and futhermore enjoyable.
Your use of acronyms and descriptive context have improved both my labs and test marks. Thank you. Love reading through everything! You make it so understandable and interesting!
I really appreciate the links to more topics too! Why is it that HF is more acidic than HI 2 , but when its connected to the carboxyl group it is I that is more acidic?
You must be used to all the gratitude by now but thank you so much! This just made everything fall into place :. These pages have been great, where can we find the answers to the problems you usually give at the end? Equilibrium tends to proceed toward the more stable product, yes? H-bonding makes the solution tightly binded. Its makes organic chemistry SO easy for me to understand! I might be missing something, so please correct me if I am!
Thank you so much for creating this easy to understand article. I was about to give up until I stumbled upon this today. Basically the same thing explained in a more elaborate slightly better way.
I had a question if you have a moment! My professor is also not very great at translating our questions in class. I have been looking for a thorough explanation like this for such a long time, being unable to find one. I had lot of problems with acidity. Now I have a better understand after reading this article. Hi I had a question. When taking inductive effects electron withdrawin and electrons donating into account are we looking at the conjugate base or the acid itself if we wanted to apply rules such as neutral N or O are considered electrons donors?
Anything which stabilizes the conjugate base will result in a stronger acid and vice versa. Please please please help. You mention two factors, electronegativity and size. Check out this post on amines. May God bless you sir. My sister had her exams and needed help. I, although being a student of commerce stream , decided that I had to help her in every way I could. But I knew I sucked at organic chemistry in school,and so did my little sister.
I found your site , and the next day I am understanding things better than I ever did ,.. Sir i am stucked please answer urgently. Hi, I found your posts extremely helpful! And how to determine the acidity of substituted aromatic compounds, such as benzoic acid?
Thanks in advance. I am having difficulty determining the relative acidity of amines and ammonium ions. In this compounds, carbon atoms may exert two effects, related to the s character of nitrogen orbitals and the electron donating properties of alkyl groups. Covered here. Your article has been very helpful and I now have actually a chance to pass my exams in general chemistry!
I just want to ask, we have to apply these factors in sequence, as you have given them or not??? I mean first the charge, after the atom etc?? All was awesome but I just confused in inductive effect when u compares acidities of halogen acid?
As electronegative difference between F and O is less as compared to OH? So how H lose? May be my question is low of standard as I m new kindly help. It really helps me understand the factors that affect acidity of molecules. Thank you so much!! This website will surely help me to get ahead, when I study during the summer time.
This site is just awesome!! Than you sir!!! It helped me a lot!! I recommend every one this site!! Hope this site gets world recognition!! Conjugate acid—base pairs. Practice: Introduction to acid—base reactions. Next lesson. Current timeTotal duration Google Classroom Facebook Twitter. Video transcript - [Voiceover] In this video, we're going to be talking about conjugate acid-base pairs. We're going to introduce the idea of a conjugate acid-base pair using an example reaction. The example reaction is between hydrogen fluoride, or HF, and water.
So hydrogen fluoride is a weak acid, and when you put it in water, it will dissociate partially. So some of the HF will dissociate, and you'll get fluoride minus ions. And then that dissociated H plus ion. So this dissociated H plus ion will get donated to our water.
So water then becomes H3O plus, or hydronium. And so this process is in dynamic equilibrium, cause it can go forward, and it can go backward, and eventually, those two rates are equal, and they're both happening at the same time. So in this reaction, we have a couple things going on, and we're gonna think about it in terms of hydrogen ions being exchanged.
So if we just look at the hydrofluoric acid, and we look in the forward direction, our HF is becoming F minus. And it's doing that by donating or losing, so I'll put a minus for losing a proton. So our HF loses a proton that forms our F minus or fluoride ion. And then we can look at that same process happening in the backwards reaction.
So if we look at the backwards reaction, which is also happening, the fluoride ion can pick up or accept a proton from somewhere.
So it can pick up an H plus, so I'll have a plus, H plus here. And so when fluoride accepts a proton, we reform our HF. So we can see that HF and F minus have this special relationship where you can form one or the other by losing or gaining a proton.
And we can see a similar relationship between water and hydronium. So, water here, we said water is accepting a proton from HF, so we see that water will gain a proton, and that will give us hydronium. In the reverse reaction, hydronium can lose a proton to reform water. So, minus H plus.
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