--%>
Assignment Help - homework help

How to calculate solutions molar conductance?

The contribution of an electrolyte, or an ion electrolyte, is reported as the molar of a conductance.


The definition of the molar conductance is based on the following conductivity cell in which the electrodes are 1 m apart and of sufficient area that the cell holds the amount of solution that contains 1 mol of solute. The conductivity of such a cell is the mole conductance.

A of solution of concentration c, expressed in moles per litre, has a volume in litres per mole of 1/c or a volume in cubic meters of (10-3 m3 l-1)/c. a cell with this volume and electrodes separated by 1 m would be equilivalent to (10-3 m3 l-1)/c unit cells placed alongside each other. The conductivity of such a cell, which is the molar conductance, is given by:

A = 10-3 m3 l-1/c × k

This relation defines the molar conductance in terms of the specific conductance. The concept of the cell holding solution of volume (10-3 m3 l-1)/c is introduced only to suggest the definition of conductance and in practice one uses any convenient conductance cell, measures R, and calculate L = 1/R. with this datum one obtains k= (cell constant) L and finally A.

Many precise measurements of molar conductance were made by Friedrich Kohlausch and his coworkers between about 1860 and 1880. 

On the basis of such data and in the absence of any satisfactory theory about the nature of conduction in these solutions, some variable empirical relations were concluded. It was recognized that for some electrolytes plotting the molar conductance of an electrolyte at a fixed temperature against the square root of the concentration led to the plots which confirmed very closely at the lower concentrations to straight lines. Such plots for new electrolytes are lead to essentially linear plots are now classed as strong electrolytes, and those which seem to approach the dilute solution limit almost tangentially are classed as weak electrolytes.

An important relation can be deduced from extrapolations of the strong electrolyte data to infinite dilution to give what are known as limiting molar of the independent migration of ions. The law is more easily stated and understandable if some later ideas are anticipated and the conductance of an electrolyte at infinite dilution is treated as being made of contributions from the individual ions of the electrolyte. Let v+ be the number of positive ions and v - the number of negative ions implied by the formula of the electrolyte. 

Molar conductances ? in Ω-1 m2 mol-1 in aqueous solution at 25° C (values for c = 0obtained by extrapolation or, for HAc and NH4OH, by a combination of extrapolated values):

c NaCl KCl HCl NaAc CuSO4 H2SO4 HAc NH4OH
0.000 (0.012645) 0.014986 0.042616 0.00910 0.02661 0.08592 0.03907 0.002714
0.0005 (0.012450) 0.014781 0.042274 0.00892 0.02304 0.08262 0.00677 0.0047
0.001 0.012374 0.014695 0.042136 0.00885 0.01666 0.07990 0.00492 0.0034
0.010 0.011851 0.014127 0.041200 0.008376 0.01010 0.06728 0.00163 0.00113
0.100 0.010674 0.012896 0.039132 0.007280 0.00586 0.05016   0.00036
1.00   0.01119 0.03328 0.00491        

   Related Questions in Chemistry

  • Q : Net charge of a non-ionized atom

    Describe the net charge of a non-ionized atom?

    		•
  • Q : Pressure Phase Diagrams The occurrence

    The occurrence of different phases of a one component system can be shown on a pressure temperature. The phases present in a one line system at various temperatures can be conveniently presented on a P- versus-T diagram. An example is pro

    		•
  • Q : What are methods of phenol preparation

    Phenol was initially obtained by fractional distillation of coal

    		•
  • Q : Explain the molecular mass with respect

    During the formation of polymers, different macromolecules have different degree of polymerisation i.e. they have varied chain lengths. Thus, the molecular masses of the individual macromolecules in a particular sample of the polymer are different. Hence, an average value of the molecular mass is

    		•
  • Q : Problem on physical and thermodynamic

    The shells of marine organisms contain calcium carbonate CaCO3, largely in a crystalline form known as calcite. There is a second crystalline form of calcium carbonate known as aragonite. Physical and thermodynamic properties of calcite and aragonite at 298

    		•
  • Q : Group Cations Explain how dissolving

    Explain how dissolving the Group IV carbonate precipitate with 6M CH3COOH, followed by the addition of extra acetic acid, establishes a buffer with a pH of approximately

    		•
  • Q : Describe physical adsorption and its

    When the forces of attraction existing between adsorbate and adsorbent are van der Waal's forces, the adsorption is called physical adsorption. This type of adsorption is also known as physisorption or van der Waal's adsorption. Since the forces existing between adsorbent and adsorbate are very w

    		•
  • Q : Alkaline medium The amount of KMnO 4

    The amount of KMnO4 required to prepare 100 ml of 0.1N solution in alkaline medium is: (a) 1.58 gm (b) 3.16 gm (c) 0.52 gm (d) 0.31 gmAnswer: (a) In alkaline medium KMnO4 act as ox

    		•
  • Q : Molarity of solution Help me to go

    Help me to go through this problem. When 7.1gm Na2SO4 (molecular mass 142) dissolves in 100ml H2O , the molarity of the solution is: (a) 2.0 M (b) 1.0 M (c) 0.5 M (d) 0.05 M

    		•
  • Q : What do you mean by the term medicine

    What do you mean by the term medicine dropper? Explain briefly?

    		•