Classification of Acids | Chemistry

Classification of Acids | Chemistry


Hello students, we’ve already learned about acids in our previous lessons. In this lesson, we shall see how acids are classified. We know that acids are substances which are sour to taste and you also know that acids are called acids because they produce H+ ions in water. Now, depending upon these H+ ions, we classify acids on the basis of the strength of the acids and we can also classify acids on the basis of its basicity. Now, you must be wondering what is basicity of acids. Now basicity of acids means if we have one molecule of an acid how many H+ ions it can produce. So, basicity depends upon the number of H+ ions that can be produced by one molecule of the acid. And, what about the strength of acid. It depends upon the concentration of H+ ions. concentration of H+ ions Okay, now what is concentration of H+ ions? It means that, if we have some amount of acid, then from that amount of acid how many H+ ions can be formed. That becomes a concentration of acid. Let us learn about this in detail. Okay, now depending upon the strength of the and we can divide acid into being strong acid and into being a weak acid and depending upon the basicity we can divide acids as Monobasic, then we can divide as Dibasic and Tribasic. Okay, let’s first start with what are strong acids? We start off with what are strong acids. Okay, let’s take an example of a very strong acid. HCl and we dissolve HCl in water so it is aqueous. Now suppose, if we have hundred molecules of HCl, when hundred molecules of HCl dissolve in water, all the hundred molecules split due to which we get hundred H+ ions and hundred Cl- ions and both are aqueous. Okay. This is called a strong acid because the entire hundred molecules of HCl have split and they’ve given us hundred H+ ions, that means they dissociate completely. So, such as they’re called strong acids. So that means, if acids dissociate completely, then they are termed as strong acids and they give more number of H+ ions. Let’s take the example of another acid. We have H2CO3. This is the carbonic acid. Okay, now suppose if we have hundred molecules of carbonic acid. Now hundred molecules of carbonic acid won’t split completely. Some of them will split about 20 to 30. So, we get about 20 to 30 ions of H+ and 20 to 30 ions of CO3 2 minus and because there are two H+ we balance it. Now in this case, not all the hydrogen’s have split to become H+, only some of them have. Due to which the hydrogen ion concentration in this case is less. So we say, these acids that weak acids because they do not dissociate. So, they do not dissociate completely. Okay, if they are not dissociating completely, that means they are weak acids. So, you can see the difference between the two. If we have taken hundred molecules of HCl, all 100 have split and we get 100 H+ and instead of getting H+ in this case, we are getting some 20 to 30 H+ ions and if you doubled them, it becomes some around 40 to 60 H+ ions from so many molecules available. So, we can see this acid is a weak acid and this acid is a strong acid. Now, let’s move ahead with the basicity. Now, basicity of any acid means how many H+ ions can be produced from one molecule of any acid. Now suppose, if we have HCL. HCl will split into H+ and Cl-. So, we get only one H+ from one molecule of HCl. So, this is called a Monobasic acid. That is because there is only one H+ that has to be neutralized by your base. So, this is called Monobasic. Now second, if we have example of H2SO4, Sulphuric acid. Now sulphuric acid, will produce H+ and SO4 two minus because hydrogen is only one electron but SO4 accepts 2. So, that is why we need 1 more hydrogen ion. So, there are. So if from one molecule of H2SO4 we get 2 H+ions, so this acid is called Dibasic acid. Okay, and so that means, if we talk about this acid, there are 2 H+ ions that has to be neutralized from one molecule of H2SO4. So that is called a Dibasic acid. Then, if we have the example of phosphoric acid, this is H3PO4. This acid will give H+ and PO4 3 minus. This is because PO4 accepts three electrons, H+ donates only 1. So we need 3 H+ ions. So, from one molecule of H3PO4 we get 3H+ ions, so this acid is a Tribasic acid. This is the phosphoric acid which is a Tribasic acid. So, there are three H+ ions that can be neutralized which are produced from one molecule of H3PO4. So, this is why these are called Monoacid, Dibasic and Tribasic because we are talking about the H+ ions that have to be neutralized by a base. So, depending upon the strength and basicity of acids, the acids can be classified as strong and weak and on the basis of basicity it can be classified as Monobasic, Dibasic and Tribasic.

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