Molar Conductivity with Solved Examples

The calculation of determining the electricity flow through any solution is the solution’s molar conductivity divided by the solution’s concentration. For example,where the conductivity is known, and the concentration is known as C.

The molar conductivity symbol is referred to as Λ or Λm. 

So, from this, the formula gets derived as 

Λm = K/C

With the help of this formula, you will be able to solve many problems regarding molar conductivity and will be able to describe the factors affecting molar conductivity.

Definition Of Molar Conductivity

The conductivity of an electrolyte solution divided by its concentration is known as molar conductivity. 

The SI unit of molar conductivity is Siemens Meter Square per Mole or can be written as S m2 mol-1. 

From the definition, it is easy to understand that conductivity is based on the concentration of the solution. Therefore, the more the concentration is, the more the conductivity will be.

Not only this, there are some other factors as well.

Factors affecting molar conductivity

As for the concentration of the solution, there are some other factors as well, and these are too important to solve any problem related to molar conductivity. 

The concentration of Ions in the solution

The molar conductivity is completely dependent on the concentration of solution. Not only the solution also depends on the ions of the solution. The ions are the ones that are responsible for the conductivity. The more the ions will be in the solution, the more the solution will be conductive, and the more you will get molar conductivity.

Types of solution

An inorganic solution will always have better molar conductivity than an organic solution. This is because the ions of an inorganic solution will always be more charged, whereas the organic ions will have less charge. Therefore, ions with more charge will always be able to carry more electricity.

Temperature

The temperature may not be a big factor, but it is significant in molar conductivity. The molar conductivity symbol and its formula directly don’t relate to temperature. But, with the increase in temperature, the conductivity of a solution increases. Warmer water has more molar conductivity. 

With a change of the temperature of 1o C, the conductivity gets changed by 1.9%. Therefore, the ideal temperature for calculating molar conductivity is 25o C.

Solved Examples

• What will be the molar conductance of 0.025M aqueous solution of calcium chloride at 25oC? It is given that the conductance of calcium chloride is 12.04 x 10-2 Sm-1

With the help of the molar conductivity symbol, this can be written as 

Λm = k (Sm-1) x 10-3 / M mol-1 m3 

     = (12.04 x 10-2 Sm-1) x 10 mol-1 m3 / 0.025

     = 481.6 x 10-5 S m2 mol-1

The unit of molar conductance is S m2 mol-1.

The calculation for the molar conductivity will always be at a certain temperature, and it will be at 25o C.

Or else, the temperature should be compensated by 1.9% for each degree C. 

For any experiment, if the temperature is not near 25o C, the result is not reliable.

There can be one more type of problem,

• What will happen if you store copper sulfate in an iron vessel for longer?

It is given that Ecu 2+|cu = 0.34 V and EFe 2+| Fe = -0.44 V.

Ans. ( Eoxo)Fe|Fe2+ = 0.44 V and( Eredo) cu 2+|cu = 0.34 V.

The positive emf values show that the iron will be able to oxidize the copper, and it will reduce. In other words, the vessel dissolved.

So, it is not possible for copper sulfate in an iron vessel for longer.

There can be one more type of problem.

Question: There are two metals, M1 and M2. which attain potential values of reduction as –xV and +yV. Which liberates H2 from H2SO4?

Ans; The metal with high oxidation potential will liberate H2 from H2SO4. So, the metal with a positive charge is, M1 will have more potential to do so.

Conclusion

Solved examples of molar conductivity can be of different types. They can be numerical or logical. Also, it can even be of explanation type. With the help of the molar conductivity symbol and its formula, it is easier to solve the problems.  

Also, all the factors should be kept in mind while solving any problem to minimize the error. Even during any experiment, it is necessary to keep all the factors in mind to eliminate any error.

Before keeping any solution in any metal box, you need to check the oxidation power and the molar conductivity of one of the substances. Or else it will react and get dissolved.