What are weak acids?

 Hello fam, we are back again today! In today's lesson, we want to understand the concept of a weak acid. When we were children, we always made fun of other children that appeared physically feeble. Some times, we even taunted them and many of them were too frail to resist such harassment.


The lack of physical strength on the part of the feeble looking children was regarded as weakness. Let us keep this picture in mind as we review our lesson of yesterday. 


In our lesson yesterday, we saw that an acid that can dissociate completely in solution is called a strong acid. If on the other hand the acid does not dissociate completely in solution? Then the acid is a weak acid. This is a akin to the weak child that does not respond when harassed. The weak acid does not respond when harassed by water!


We define a weak acid as any acid that does not completely dissociate when dissolved in water. In other words, there would be a substantial amount of the molecules of the acid left in the solution after the acid has been added to water. 


To put it in a much simpler language, only a small amount of the acid does break up in water solution to form ions while the whole molecule largely remains undissociated.


Let me give you an example, consider the dissociation of ethanoic acid in water as follows;

CH3COOH(aq) ---->CH3COO^- (aq) + H^+(aq)


Laboratory evidence shows that only about 0.132% of ethanoic  acid dissociates in solution and that there is a large amount of the undissociated acid left in the solution. 


Since there are more molecules than ions in a weak acid solution, the weak acid solution does not conduct electricity quite well. 


Solutions of strong acids conduct electricity quite well due to the presence of many ions in it hence such solutions are called strong electrolytes. Solutions of weak acids do not conduct electricity quite well due to the fact that the ions in them are few. Solutions of weak acids are therefore called weak electrolytes.


In conclusion, many mineral acids are often strong acids while all organic acids are weak acids. There are exceptions though, H3PO4 is a mineral acid yet it is a weak acid.


Hope you enjoyed our lesson today?


Follow  our page  and share!


Do you have assignments, term papers, projects and difficult homework questions? Contact us for help now! We also offer home and remote tutoring services to students at all levels in science subjects

Comments

Post a Comment

Popular posts from this blog

Strong and weak Bases

Image
 Hello! Welcome to today’s lesson. Today, we would consider the idea of strong and weak bases. We have previously considered the idea of strong and weak acids(see the page timeline). We said that a strong acid is an acid that dissociates completely in solution while a weak acid is an acid that does not dissociate completely in solution. We said that the percentage dissociation of a weak acid may be as low as 0.3% at about 1 M concentration of the solution. On the other hand, a strong acid may attain a 100% dissociation in solution. A similar scenario applies to bases also. A strong base is a base that dissociates completely in solution. A weak base is a base that does not dissociate completely in solution. When we talk about the dissociation of a specie, we are talking about the break up of the specie into its constituent ions. Now consider the hypothetical base HB. The base would be dissociated as follows; HB(aq)  --> H^+(aq) + B^-(aq) This dissociation may also be called ...
Read more

pH range of color change for indicators

Image
 The pH range of color change for an indicator is the range of pH values over which the indicator changes color. Different indicators have different pH ranges of color change. Let me quickly remind you of something that we established in the last lesson. We saw that the pH at which the color change occurs must be the point at which pH = pKin (check the page timeline for details of the previous lesson). At this point, the color change is observed in the system and the color change usually spans through two pH units. It then follows that if we know the pKin of the indicator, we can be able to establish the pH range by counting two pH units around the value of pKin of the indicator. Let me also state that the pKin is the same as the pKa of the indicator. Let us look at phenolphthalein or instance; the pKa (pKin) is 9, the pH range is 8 – 10. For methyl orange; the pKa(pKin) is 3.5 while the pH range is 3 – 5. Finally let me say this; the pH range of color change for an indicator is de...
Read more

Lewis Acids

Image
 Hello, welcome to today’s lesson. I believe that this series is making a lot of sense to you. Yesterday, we showed that in order to have a substance behave as a Lewis acid, then the substance would have to possess a central atom that has an empty orbital into which it can be able to receive an electron pair. We can never stop repeating this fact because it is the most fundamental fact that you need to know about Lewis acids. We also showed that BF3 and AlCl3 could all act as Lewis acids because we established the fact that there is a free 2pz and 3pz orbital on the central boron and aluminum atoms respectively. This is the orbital into which the electron pair is received when the BF3 or AlCl3 acts as a Lewis acid. Here we have shown the reaction of ammonia with BF3 and AlCl3. In either case, we can see that what is going on actually the formation of a dative or coordinate covalent bond (Refer to the earlier lesson on the formation of H3O^+ ion). The ammonia molecule has a lone pa...
Read more