Chemistry Class XII Conductance & Molar Conductance

Added: 2026-05-31

[00:00:00]Good morning students. Today we will discuss about the conductivity, molar conductivity, equivalent conductivity, and degree of dissociation and dissociation constant, which is the part of electrochemistry chapter.

[00:00:29]Okay.

[00:00:30]First of all, we will discuss about the conductivity.

[00:00:39]Conduction shown by the simple solution is called conductivity, which depend on the concentration.

[00:00:46]When we increase the concentration, the conductivity also increases because the number of ions also increases in the solutions. Ions are responsible for the conduction for electrolytic solution.

[00:00:59]Next, we will discuss about the limiting molar conductivity and molar conductivity, equivalent conductivity.

[00:01:07]Then, let's go molar conductivity.

[00:01:16]Molar conductivity.

[00:01:27]What is molar conductivity?

[00:01:30]Conducting power of all the ions produced when the 1 mole of the electrolyte dissolved in the solution.

[00:01:37]It is denoted by lambda m.

[00:01:41]So, lambda m is equals to k into 1,000 upon c, where c c is the concentration.

[00:01:58]Concentration.

[00:02:00]and K conductivity The SI unit of molar conductivity is Simon centimeter square per mole.

[00:02:20]Are you there?

[00:02:23]Is that clear?

[00:02:25]Conductivity molar conductivity is defined as the total number of ions produced when the one mole of the electrolyte dissolved in the solution.

[00:02:36]It means you have to make one mole of the electrolyte water dissolved here. It may give me ions produced here. What ions give me conduction here? What can I give you?

[00:02:47]Molar conductivity, right?

[00:02:50]Any doubt?

[00:02:51]Or lambda M is equals to K into thousand upon M. Where M?

[00:03:04]Molarity.

[00:03:10]Molarity.

[00:03:12]SI unit same for both. Okay?

[00:03:16]I will talk to you again. What is the effect of the concentration on the molar conductivity?

[00:03:25]What is the effect of the concentration on the molar conductivity? Then concentration increases what is the effect on the limiting molar conductivity?

[00:03:39]You know concentration is inversely proportional to the molar conductivity. Then we increase the concentration, the limiting molar conductivity decreases because these are inversely proportional to each other.

[00:04:00]Concentration increases, limiting molar conductivity decreases.

[00:04:05]Conductivity increases, then molar molar conductivity increases. Any doubt? Then next we will discuss about the limiting molar conductivity. Limiting molar conductivity calculated with the help of Kohlrausch's law.

[00:04:24]Limiting molar conductivity calculated with the help of Kohlrausch's law.

[00:04:36]According to According to Kohlrausch's law According to Kohlrausch's law, the limiting molar conductivity of an electrolyte at infinite dilution is equals to the limiting molar conductivities of their ions. It means cations and anions. It is denoted by lambda naught m.

[00:05:29]So, we will take any example.

[00:05:33]Limiting molar conductivity of NaCl.

[00:05:39]So, it is equals to the sum of the limiting molar conductivities of their cations plus anions.

[00:05:48]So lambda not M H positive plus lambda not M Cl negative.

[00:05:56]These values given in the question paper. These values given in the question paper.

[00:06:03]Right? So, we add then calculate the limiting molar conductivity of any electrolyte.

[00:06:10]Or lambda not M NaCl is equals to lambda not Na positive plus lambda not Cl negative.

[00:06:25]If the limiting molar conductivity of M MgCl2 the molar conductivity of Mg2 positive plus molar conductivity of 2 Cl negative.

[00:06:46]The stoichiometric coefficient of the anions multiplied by the limiting molar conductivity of their ions.

[00:06:55]Or lambda not M AlCl3 lambda not M AlCl3 is equals to lambda not M Al3 positive plus lambda not M 3 Cl negative.

[00:07:15]Clear?

[00:07:18]Listen, if the conductivity of Cl ion is given, then in case of AlCl3, Al3 positive and 3 into limiting molar conductivity of Cl negative. Is that clear? Any doubt?

[00:07:34]It is the Kohlrausch's law. Listen again, according to Kohlrausch's law, the limiting molar conductivity of an electrolyte at infinite dilution is equals to the sum of the limiting molar conductivities of their ions. It means cations plus anions.

[00:07:55]Clear?

[00:07:56]Next.

[00:07:58]Equivalent conductivity.

[00:08:01]Equivalent conductivity.

[00:08:21]It is denoted by lambda eq.

[00:08:29]Equivalent conductivity same of molar conductivity. There is no big difference between the molar conductivity and equivalent conductivity. Listen.

[00:08:40]Molar conductivity.

[00:08:44]Molar conductivity is defined as the conducting power of all the ions produced when the one mole of the electrolyte dissolved in the solution.

[00:08:52]Same of equivalent conductivity is defined as the conductance of all the ions produced when 1 g equivalent of the electrolyte dissolved in the solution. It is denoted by lambda eq.

[00:09:09]Any doubt?

[00:09:11]Lambda eq is equals to K into 1,000 upon N.

[00:09:23]Where N? N is the normality.

[00:09:28]Normality.

[00:09:34]Normality is defined as the gram equivalent of solute per unit volume of the solution. The SI unit of same of molar conductivity.

[00:09:46]Simon centimeter square per mole.

[00:09:51]Any doubt?

[00:09:53]Any doubt in molar conductivity, boys?

[00:09:56]Limiting molar conductivity and equivalent conductivity. Let's recap.

[00:10:01]Molar conductivity is defined as the conducting power of all the ions produced when the one mole of the electrolyte dissolved in the solution.

[00:10:11]After one mole of the electrolyte after you solution may dissolve kar diya. Usne kitne number of ions produced here usse kitna conduction hua hai woh kya hai uski molar conductivity.

[00:10:22]Then, limiting molar conductivity.

[00:10:25]Limiting molar conductivity limiting molar conductivity calculated with the help of Kohlrausch's law.

[00:10:47]According to Kohlrausch's law the limiting molar conductivity of an electrolyte at infinite dilution is equals to the sum of the limiting molar conductivities of their ions.

[00:11:01]It means cations plus anions. It is denoted by lambda naught m.

[00:11:07]Lambda naught m HCl is equals to lambda naught H positive plus lambda naught Cl negative.

[00:11:19]Is that clear?

[00:11:20]Next.

[00:11:22]Equivalent conductivity also explained.

[00:11:26]Equivalent conductivity is defined as the conducting power of all the ions produced when the 1 g equivalent or 1 g electrolyte dissolved in the solution.

[00:11:38]It is denoted by lambda eq. Next.

[00:11:42]Next.

[00:11:43]We will discuss about the degree of dissociation. Are you aware of the degree of dissociation?

[00:11:50]No. Degree of dissociation is defined as the weak electrolyte dissolved in the solution. How many percent dissociated in solution is called degree of dissociation. It means after we put weak electrolyte water in the dissolved here, how many percent dissociated will be there degree of dissociation. But here, degree of dissociation is different from this.

[00:12:17]It is the ratio of molar conductivity and limiting molar conductivity.

[00:12:24]It is denoted by alpha.

[00:12:29]Degree of degree of dissociation.

[00:12:55]Degree of dissociation is the ratio of molar conductivity and limiting molar conductivity.

[00:13:03]alpha ratio of molar conductivity and limiting molar conductivity.

[00:13:36]It is denoted by alpha.

[00:13:44]Alpha is equals to molar conductivity and limiting molar conductivity.

[00:13:53]It gives the ratio between molar conductivity and limiting molar conductivity.

[00:13:59]Right?

[00:14:01]Then, dissociation