Question

please answer all parts of this question

2. Consider the junction potential a. Describe how and why a junction potential occurs. What is the error, in terms of concentration, if a junction potential changes the true b. cell voltage by 1.50 millivolts in a potentiometric determination of an analyte? Show the relevant calculations. c. Describe at least one way in which the error due to a junction potential can be eliminated or at least significantly reduced.

Answer 1

Ansuer:- pageO a) Describe how and why a junction potential occurs:- differen t with a When two electro lytic solutions comporition are in contact, a potential through the inter face is formed. This is due to the unequal distribu hion of charged species that have different electric mobilities, it is to say, differences in the rate of diffusion- Then, the separation of charges generates a potential called Junch'on potential. b) Eror in terms of concentration in a potentiometri c determination :- In direct potentiometa'c determination of an analyte, exact concentration is given by, "CEcel -k) (x] = to 0.0592 where (x] is the Concentration of analyto x. n is the number of electrons transferred: Ecel is the cell potential measured CS Scanned with CamScanner k is the electrode constant.

page@ When junction potential CE) in the dectrade constant is not cansidered, equation 0 gives: nC Ecel -k E;) [x] error = 10 O.0592 The Quantitative error is givern by: [x] error •%. error X (00 [x] substituling equations O and @,ue have : 10 CEcel -k- E) O. 0592 % error = X100 1o"CEcel -k) O.0592 it Can be Simpli fied as : -n Ej (1-10 05) xl00 X 100 %. error = 0.0592 substituting n =1 mol of electrons Eg = 1,50 mV = I:50 X 103 V is : The error in terms of Concentrahion Scanned with CS CamScanner 1.50 X10-3 X 100 % error = (1-10" 0.0592

page@ % error =5-66 %. - 5:7 % C Why to reduce eror due to the junction polential :- The ux of a slt bridge of concentrated electroly tic solution between the (wo solutions Can reduce Succes fully the junction potential and it can be Congidered as Zero. CS Scanned with CamScanner