Question

A Mg* liquid membrane ISE and a Ag/AgCl reference electrode were mL of solution containing an unknown concentration of Mg2+. The cell voltage was +0.4960 V. Without removing the electrodes, 10.0 mL of 5.0x10-2 M Mg was the solution and mixed. The new cell voltage was +0.5025 V. Assuming that the Mg has an ideal slope of 0.02958 V; calculate the original Mg2+ concentration.

Answer 1

Sol The elatonShip be-toeen the aetivty of on and eleciTode Polential e ?s gven by 'Nenst Equation. E- E Ca.303 RT/AF) log) E Eleciode Cin mv) betoeen the ISe and Potential A3/Agcl efesen ce electso de e 0 Standaad eduction poten tial Cin m) of a Particular ISedeference electTode Pas 6.314 Jmol-k Constant R Ideal TTempesature in kelvin Caenesally asc (ak) Chage On the TonCta) F= Fasaday Constant C96500 cmo1) ogathm of the activit of ton n 2 Constant €R, T,n,F ase Thus Er A lence fo the E Vs oplot B ') be the Slpe

Lets the Concentaation -to be x, and unknoon Ofte addition or lo ml of 5,0 x 0M the Concemtation is y. €1A Blo ) B = O.o2958 V 29.5 mv E + o.4960 V 496mv Thus A a.5 0 x) = u96mv The electsode Poten tial inthe Second Concentuation Concentation Of Ond aftes addtion Of Knoon ea eAtBlo CV) t0.5025V 50a.5 mv B 29.5 mv Thus 50a.5 mv 2 A+a9.5

Suibtsacting Equation fo uation a.5 log C-a.5 log C)- 6.5 6.5 a9.5 OaQo శిషం 1.66 y .66x (mm) When Concentoation of TOML of Which has 5.0x10 5 otha5ML of Which ized has Concentiaton mM, hea Concentsaon for the bapplying Knoan Solution is obtoined the Intial Volume, CmL) lo mL Va Final Volume (as+1o = 35mL) 5.00 x0 = 5.0 x 10 mm Ca? 5 メ10 5.0X10 35 5 43 X10 mm

-The Unknoo Solution Oould be Concentoa ted Cas 35 Concen tation - o.1imes) Then nea OJI4 mm un known. Y. Co-y 1.43 10mn .66 -5 J.66 = O.TI4 t 1.43 X10 .43x10 CLCC-O-N 5 -5 =.5 xO O.946 .5 1 'm