TO DETERMINE THE EQUIVALENT CONDUCTANCE OF ACETIC ACID AT DIFFERENT DILUTION AND TO VERIFY "OSTWALD'S DILUTION LAW" FOR ACETIC ACID AND TO DETERMINE ITS IONIZATION CONSTANT

 

APPARATUS REQUIRED

• Conductivity cell & bridge

•  Volumetric flask, 

• beaker

CHEMICALS REQUIRED

• O.1N KC Solution 

• O.1N CH3COOH Solution 

PRINCIPLE

Ostwald's dilution law states that the degree of ionization of weak electrolyte increases with the increase of dilution. i.e. with the decrease of concentration given temperature 

To verify the law, the equivalent conductances of the given weak electrolyte eg. acetic acid are determined at different concentration with the help equation.

Λ.qv = K×1000÷C

where k = specific conductance

observed conductance (X) cell constant

C = concentration of electrolyte in normality.

and Req: eqv. conductance of a solution containing 1gm eqv. of electrolyte. The degree of acetic acid is calculated in case ionization 'x' of by using equation

X=. Aeg÷Λ.

where Á. equivalent conductance at infinite dilution

Λ.= Λ.H + + Λ. CH₂COD" = 390.74

as to The degree of ionization of acetic acid at different dilutions are then compared graphically so verify dilution law and also the ionization constant Ka of acetic acid is determined in each case by using equation

ka = x²C ÷ (1-x)

PROCEDURE

The instrument was first standerized and the cell constant was noted after calibration. Acetic acid of different concentrations (0.002, 0·005, 0.01 0.02 and 0.05 N) were prepared by the accurate dilution of the 0.1 N stock solution were using conductivity water. The conductances of each solution were observed from conductometer using conductivity cell of 1 cell constant. equivalent conductance, degree of ionization & ionization constant for each case were calculated.

The dilution law was verified graphically by

X verses 1/√C plotting

OBSERVATION

The cell constant of the cell (L) = 1

The equivalent conductance of acetic acid of infinite dilution :- 

Λ. = Λ.H+ + Λ.CH7COO-

= 349.82 +40.9

= 390.74

Mean value of ka = 2.53×10-5

CALCULATION

Specific conductance (k) = Ross x L

Req = kx 1000/C

X= λen/λ°

Ka = x²C/1-X

Graphical Representation

We have, ka= x²C neglecting X compared to 1

or X = √ka÷c

X verses 1/√c was plotted from graph, the value of ka: 1.51 X 10-5

RESULT

 Hence the value of ka for acetic acid was found to be 1.51 X 10-5 graphically

CONCLUSION

The equivalent conductances of acetic acid at different dilution can be determined and Ostwalds dilution law Also can be verified for acetic acid and ionization constant also can be determined.