# Chapter 15_electrolyte acid base

**Channel:** Chem_Kwon
**Source:** https://www.youtube.com/watch?v=0wdH1z3dxiQ
**Transcript page:** https://www.withtranscript.ai/video/0wdH1z3dxiQ

## Chapters

- 0:00 — How Salt Dissolves in Water
- 3:59 — Non-Electrolytes and Conductivity Basics
- 7:22 — Acids, Bases, and Hydronium Ions
- 11:00 — Strong Versus Weak Acid Species

## Transcript

**[0:00]:** So we know from our previous experience, when you add salt crystals in water, it dissolves. And what does that mean in microscopic view? So this is a image of the salt crystal in water solution. So you see the salt is composed of the sodium ion and chlorine ion which is surrounded by the water molecule. So what happens is that water molecules surround the positive and negative ions and helping them move away from their position in crystals. So the water molecule pulls these ions apart and once once one of the ions are pulled away, then the other ions are exposed by the water and that's how the dissolving process continues. And when you look at this, the ions um the the orientation of water molecule is different for the anion and cation. It's because water molecule has partially positive end and partially negative end. So the partially positive end of water molecule orient towards the negative ion and partially negative end of water molecule orient towards the positive ion.

**[1:18]:** So because of this partially positive and negative side of the water molecule, which can compensate the attraction between the ions and makes them actually dissolve in water and have the ion forms. I want you to watch this two links. One is Parsons sodium chloride dissolve animation. So it's a animation of the images that I showed you in previous slide. And the second one is molecular dynamic animation. This is the theoretical chemist um calculation on how these ions or molecules behave. Not molecules break into ions in the solution. Molecular covalent compounds don't break into ions, and some ionic compounds um only dissociate partially in solution. So let's have a look at um the electrolytes. So electrolytes are the ions that conduct electricity, which means um when this um salt breaks into in water, it breaks into ions. And because it's a charged particle, it can actually conduct electricity.

**[2:35]:** There's like plus and minus charges around these um salt crystal. Um and stronger electrolyte means there's more conductivity, which means there's more ions present in the solution. Weak electrolytes are the one that does dissociate into ions. So acetic acid breaks down into a acetate ion and um hydrogen ion, but they do go back to the acetic acid form because a formation of uh acetate ions and hydrogen ions are less stable compared to the like copper and chloride in copper chloride solution. So acetate ions and hydrogen ions go back to the acetic acid form. So if you look at the solution inside, there are some presence of the hydrogen ion, and there's um acetate ions, but some of the acetic acid molecules are present, right? So there are only few of the positive and negative charged particles in the solution. So it will conduct less electrolyte uh less conductivity.

**[3:54]:** It will be less conductive than the stronger electrolyte.

**[3:59]:** Non-electrolytes are the covalent compounds or molecular compounds where it does not dissociate into ions. So, it just becomes a homogeneous mixture of solution, but not um ions. So, let's let's review. Strong electrolytes are characterized by complete dissociation in water, which means it breaks down into ions in water. Weak electrolytes dissociate to a much smaller extent. So, there's only smaller portion of ions present in the solution because majority are um back into the original form like this acetic acid here. Non-electrolyte does not dissociate at all, so it does not conduct any electricity because there's no charged particle present in the solution. Strong electrolytes are the substances break up to produce many ions in water. Many ions present to move electron and therefore it conducts electricity. So, uh most of the strong acids and strong bases are part of the strong electrolytes because it does break into ions completely.

**[5:11]:** So, like example um potassium hydroxide breaks into potassium ion and hydroxide ion and hydrobromic acid actually breaks down into hydrogen ion and bromide ion. So, um you need to remember these strong acids and strong bases because these are going to be the strong electrolyte means it completely dissociate into ions and it is soluble in water. Weak electrolytes are the substances that are weak or poor conductor of electricity because these substances mostly remain intact as compound and producing a very few ions in water. So, only a few ions present to move electron, therefore conducts electricity less compared to the strong electrolytes. So, the key indicator for the weak electrolyte is this reverse arrow. So, um the the reaction is going forward and some of the reaction actually go back to the original form. Because the ions present in the solution are less stable, therefore it wants to go back to the stable form, which is the um nitrous acid, for example, in this example.

**[6:33]:** And um so this reverse arrows or this um double arrows going back and forth is the indicator tells you that it's a it's a weak electrolyte. Non-electrolytes are the substances do not conduct electricity because the molecule does not break into ions. And uh most of the molecular compounds or covalent compounds are non-electrolytes. For example, here, sugar does not break into water. It just dissolves in water, become a sugar water. But the sugar molecule actually do not break into ions. So therefore there's no electrons. Therefore there's um it doesn't conduct electricity.

**[7:22]:** So now let's do electrolytes and conductivity. The ability of solution to conduct electricity is regarded as evidence that it contains ions. So all soluble salts are strong electrolytes. Slightly soluble salts are weak electrolytes. Strong acid bases are strong electrolytes. Weak acid and bases are weak electrolytes. Insoluble compounds are non-electrolytes and molecular compounds are non-electrolytes. Acid base can be either strong or weak electrolyte because acid is a substance that produces the hydrogen ion in water. So um for example, hydrochloric acid when it dissolves in water, it breaks into hydrogen ion and chlorine ion. Or nitric acid can break down into uh hydrogen ion and nitric ion. And some of the um acid are monoprotic, which means it can only generate hydro one hydrogen ion per molecule. Like example here, hydrochloric acid or nitric acid. Some are polyprotic means there are more than one hydrogen present in the molecule so it can release more than one hydrogen per molecule.

**[8:44]:** So a good example is the phosphoric acid like H3 PO4 where um phosphoric acid contains three hydrogens. So technically it can release three of the hydrogen ion. Um some of the properties for the acid are it tastes sour, it neutralizes base, it reacts with the carbonate ion or bicarbonate ion to produce carbon dioxide. It can react with metal to produce H2 and it turns blue the litmus paper to red. So litmus paper is like a strip of paper that tells you the pH level of the solution, which just basically tells you acidity or basicity of the solution. So it turns the blue litmus paper in red. So you you can see the litmus paper in chemistry lab um maybe in chem Um one thing to note about the acid is that when acid dissolves in water, it actually generates this which is the hydronium ion, so

**[9:58]:** H3O+ which is the hydrated proton. Um so H+ from the acid, right? Reacts with water to form hydronium ion. And since the hydronium ion is basically H + 2 + water, we can simply say H + instead of H3O + so which means um it's the same thing. It just reacts. It it really exists as a hydronium ion in the solution. For for simplification, we just use hydrogen ion. So you can write HCl + water to form hydronium ion + chlorine ion or you can simply say HCl dissolves into hydrogen ion and chlorine ion. So this is the same thing as H3O +

**[11:00]:** So strong acid ionizes or dissociates almost completely in an aqueous solution and loses its proton readily. Proton is the H + another another way of saying hydrogen ion is proton. And um strong acid are excellent conductor of electricity because their major species are ions. So major species are the chemical particle present in the greatest abundance in acid solution. And the minor solution uh species in strong acid are un-ionized molecules. So it's a chemical particle present in lesser abundance in acid solution. So for example, then strong acid here which is the strong electrolyte has um ions present in the solution. You see the hydrogen um hydronium ion which is H hydrogen ion or it's also called proton. And you have the anion part um surrounded by the water molecule. Weak acid uh ionizes only slightly in the aqueous solution and does not release proton readily. So the uh weak acid are the poor conductor.

**[12:14]:** And and the major species are the un-ionized molecule, which is the original form of the acid or base. And the minor species are the ions. So you only see few of the ions present in the weak acid or a weak electrolyte compare to the strong acid or strong electrolyte which where the majority of the particles are ionized form, right? You see all these ions present in the solution in strong electrolyte. Whereas you see less in weak electrolyte. So these seven acid are the strong acid, which means it's the strong electrolyte. And other than these seven are weak acids where it only slightly dissociate into ions. Let's do this example. Here are the list of the acid. And it tells you if it's a strong, weak, or strong acid. And you need to write the species present in when it's dissolved in water. So if it's a weak acid, not that not only that it completely dissociate into ions, but also it has the present molecule form too.

**[13:41]:** Because it's a reverse reaction, right? A lot of the weak acid is tells you that it does break into ions. Some does break into ions. But when these ions actually go back to form the acid form, right? So in the solution, we see the the molecular form present. For the strong acid, only what we only see is the ions and the water because this acid breaks into ions completely. So we don't see any of the HBr present in the solution. Oh, um phosphoric acid is a weak acid, which means it breaks into ions, right? So H + and H 2 PO 4 - and the phosphoric acid is also present in the solution because once it forms the ions, some of the ions bound back and form the um the phosphoric acid. HF is also part of the weak acid, which means um the hydrogen ion and fluorine ions are formed and some are actually bound back and form HF again.

**[15:04]:** So we see the presence of the um molecular form of the acid in the solution. So here are the distinctive difference between the strong and weak acid where strong acid does not have the um the molecular form of the compound. So HBr does not exist in this in this because HBr completely dissociated into um proton and bromide ion. Whereas the weak acid always have these um molecular form present in the solution because not all dissolve dissolves in water.