It may be defined as the conducting power of all the ions produced by dissolving one mole of an electrolyte placed between two large electrodes at one centimetre apart. Calculating the amount of a solution of given strength that must be used to prepare a solution of desired amount and strength involves the following. Determining the quantity of active constituent needed and then calculating the quantity of the available solution that will provide the needed amount of constituent. Use the alligation methods to determine relative amounts of components mixed together to make a mixture of a required strength. Determine the volume of a specified stock solution needed to prepare a given solution. Where ρ is the proportionality constant and is known as specific resistance or resistivity.

On dilution, conductivity decreases but volume containing one mole of an electrolyte increases. The increase in volume on dilution is much more than the the one which decreases with dilution is decrease in conductivity. On dilution the volume of the solution is increasing but the number of ions that carry charge in a solution remains the same.

Electrolytic conductance decreases with increase in concentration or increases with increase in dilution. This is because conductance of ions is due to the presence of ions in the solution. The greater the number of ions, the greater is the conductance. As with dilution, more ions are produced in solution so conductance also increases on dilution.

Specific conductance decreases with dilution whereas equivalent conductance increases with dilution. Where A is a constant and Λ° is called molar conductivity at infinite dilution. This equation is called Debye Huckel Onsager equation and is found to hold good at low concentrations. However at infinite dilution (i.e., when concentration approaches zero) the conductivity of the solution is so low that it cannot be measured accurately. Therefore the limiting equivalent conductivity of an electrolyte is calculated by using Debye-Huckel-Onsagar equation as explained below.

Hence the number of ions per unit volume that carry charge in a solution decreases. As the movement of these charges towards the oppositely charged electrodes causes the flow of current, the conductivity of a solution decreases on dilution. The variation of Λm with concentration, C½ is small so that the plots can be extrapolated to zero concentration. The intercept gives the limiting value of molar conductivity when the concentration approaches zero, called molar conductivity at infinite dilution, Λm. The molar conductance of strong as well as weak electrolytes increase with decrease in concentration or increase in dilution. Conductivity of an electrolyte decreases with decrease in concentration because of ions per unit volume decreases on dilution.

Explain why on dilution does the conductivity decrease whereas molar conductivity increases for an electrolytic solution. The number of ions furnished by an electrolyte in solution depends upon the degree of dissociation with dilution. With the increase in dilution, the degree of dissociation increases and as a result molar conductance increases. The limiting value of molar conductance (Λm) corresponds to degree of dissociation equal to 1, i.e. the whole of the electrolyte dissociates. The equivalent conductivity at infinite dilution (Λo) can be determined by extending this straight line to zero concentration. It is not possible to determine the value of limiting molar conductivity at infinite dilution for weak electrolytes by extrapolation of Λ versus C½ graph.


Equivalent conductivity also increases with dilution because of increase in volume containing one gram equivalent of the electrolyte. Calculating the percentage or ratio strength of a solution made by diluting or concentrating a solution of given quantity and strength entails the following. Describe the relationship of active ingredients and diluents if the amount of active ingredient remains constant and the amount of diluent is increased or decreased.

the one which decreases with dilution is

Salts such as AgCl, PbSO4, BaSO4etc dissolve to a very small extent in water are called sparingly soluble salts. Thus NaCl is known as 1-1 electrolyte, CaCl2 as 2-1 electrolytes and MgSO4 as 2-2 electrolyte. State and explain the Nernst equation with the help of a metallic electrode and anon-metallic electrode.

Conductivity of solution decreases with dilution because with dilution, concentration decreases due to which there is a decrease in number of ions/volume. For strong electrolytes, there is no increase in the number of ions with dilution because strong electrolytes are completely ionised in solution at all concentrations. Where α is the degree of dissociation, Λmc is the molar conductance at concentration C and Λm° is the molar conductance at infinite dilution.

Answer (Detailed Solution Below)

For weak electrolytes, the ‘α’ is also called as degree of ionization. The equivalent factor of the electrolyte is usually the total charge on either anions or cations present in one formula unit of it. It may be equal to basicity in case of acids or equal to acidity in case of bases.

  • Free energy is used to determine how systems change and how much work they can produce.
  • With dilution, the ions become far apart from one another and interionic forces decrease.
  • The number of ions furnished by an electrolyte in solution depends upon the degree of dissociation with dilution.
  • Win over the concepts of Chemistry and get a step ahead with the preparations for General Science with Testbook.

At this dilution, the ionization of even the weak electrolyte is complete. It is also possible to produce electrical energy by carrying out a spontaneous chemical reaction in a suitable device called galvanic cell or voltaic cell. Therefore, upon dilution, the conductivity of KCl decreases andthe equivalent conductivity of KCl increases respectively. Molar conductance of a weak electrolyte depends upon its degree of dissociation. Higher the degree of dissociation, larger is the molar conductance. The variation of molar conductivity with concentration can be studied by plotting the values of Λm against square root of concentration (C½).

Engineering Preparation

As a result, lithium salts show lower conductivities compared to those of cesium salts in water. Let us consider the V cm3 of solution containing one equivalent of an electrolyte. The cell constant can be determined by using following relations which can be derived easily from expressions discussed above. Equivalent conductivity is the conducting power of all the ions produced by dissolving one gram equivalent of an electrolyte in a solution.

The electric field exerts a force on charged particles, accelerating them in the direction of the force, in either the same or the opposite direction of the electric field. Molar conductivity For strong electrolyte can be calculated by extrapolation . Conductivity is the conductance per unit volume of the system. Enthalpy change and entropy change of a chemical reaction at 25°C are 177.0 KJ and 160.4 JK-1respectively. Calculate free energy change of the reaction and predict whether the reaction is spontaneous or nonspontaneous.

the one which decreases with dilution is

The order of a reaction refers to the relationship between the rate of a chemical reaction and the concentration of the species taking part in it. A solution of a known concentration prepared for the convenience of dispensing; usually a strong solution from which weaker ones can be made conveniently. This relationship is generally true except for volume-in-volume and weight-in-volume solutions containing components that contract when mixed together.

For a strong such as KCl, the conductance increases with dilution because on dilution the interionic forces decrease, and the ions are free to move. Molar conductance is when one mole of salt is added to form the unit volume of solution. Molar conductance is defined for a constant concentration of salt and by definition is invariant with different concentrations. Conductance on the other hand is a general purpose term and it is not mentioned without above mentioned qualifiers.

Variation of Conductivity and Molar conductivity with conductivity

In this mechanism rate of reaction depends on the concentration of alkyl chloride and KOH both. Precipitation occurs only when ionic product is more than solubility product. Number of sulphide ions produced by dissociation of H2S are lesser in acidic medium due to common ion effect. As a result only PbS is precipitated while ZnS is not precipitated. Ionic product of water can also be calculated by knowing the specific conductivity of water. Where C is the concentration and α is the degree of dissociation.

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As the temperature of electrolytic solution is increased, the kinetic energy of the ion increases. This results in the increase of electrical conductance of electrolytic solutions. Conductivity always decreases with decrease in concentration both, for weak and strong electrolytes because of the fact that ____________. While in the case of strong electrolytes (e.g. HCl) equivalent conductivity increases slowly with dilution.