WNGZWZSS0110rqql? Geneva A9| i AUTOSAVE.WKZ"0 T d1j2o8 x     @yy'()*+,-./0@ n@ Eo@ Cs@  Vx@  Cx@ f@ nf@  Vs@ A@ B@ I@ bm@  Cse@ nf2@ nfa@  ve@deltaE@00.@"Y@/%01@1@  0 0.@ .@ @0.@ 0@ .@5  2 0 00%? 00.%1@3   0  .%$@ 2 0 1%40 /%1@" Y@/%01@9  0 .%$@ 20 1%40 /%1@  0@$@4@Y@ /%0 1@ .@2.@  1%40@   1%.0.@,MbP?1@  ,MbP?1.@ @!  1%.0.@   1%1.0.@!  1%1.0. @ Geneva @  Geneva @  Geneva @  Geneva @  Geneva @  Geneva @ ] Geneva @[Simulation of standard addition method for calcium determination by ion-selective electrode @wincluding effect of interferences, perturbation of activity coefficient by standard addition, and voltage reading error @X*Boldface numbers are user-changable inputs @0 @]Reference potential?voltsEo @^Actual Nernst factorcZB?voltsnf @`Assumed Nernst factorcZB?voltsnfa @Oion charge (n)@n @a[Ca] in standard {Gz? Moles/LiterCs @Z vol. standard added@mLVs @_ [Ca] in unknown-C6? Moles/LiterCx @T  Sample volume9@mLVx @_ NaCl TISB conc{Gz? Moles/LiterCse @_ voltage reading errorMb@?voltsve @3 @mL standard added mmoles Ca volume (mL) total [Ca]Activity of Cavoltage0deltaE reading error @u 5{Gzd?59@5B-C6?5B ;{ ?%ZO? @ 5@5(\¥?5;@5B<6*%Y?5B /I?%pչZ?5KZhʷ5؄1Av @4  @0 @[Ca] by standard additionionic strength error (%)measurement error (%) % total error @b5 h?5 )p?5>wD@5 @5j>I@ @+ @0 @cDebye-Hckel calculation of activity coefficient of Ca++, in water at 25 C (c.f. lab manual, p. 47) @gAB bm for CaIonic strength (I)0log (f)0f @lʡE?BAJAB+i)+p>53?5 qҿ5ﲸO? @`after addition=5?5 $, oӿ5eǬ? @B @f%]Effect of ion interferences from impurities in commercial NaCl ionic strength buffer solution @& Ion  Atomic weight selectivity constant * charge g/mL in solution **  M in solutionactivity in solutionaa=activity equivalence @q' H+ T㥛 ? cA ? A Hz>%Ax✜]k>%A>X/[> @}( Zn++ )\XP@  @ @ %A %A%A @}) Fe++ K@ ? @ %A %A%A @}* Pb++ fffffi@ 333333? @ %A %A%A @}+ Cu++ fffffO@ 333333? @ {Gz?%A  t'y>%AVk,jj>%A4O> @}, Ni++ YM@ {Gz? @ %A %A%A @}- Sr++ HzU@ {Gz? @ %A %A%A @}. Mg++ L8@ {Gz? @ 4@%A -?%A?%A('> @}/ Ba++ )a@ {Gz? @ %A %A%A @|0 Na+ = ףp6@ -C6Z? ? Y@%A  Xڤ?%A--B?%Ac v#> @U1"* from the electrode's spec sheet AA%Av4wſ> @"2** from the reagent label2 տq  Chicago Geneva @d,Type in values for the sample concentration Cx, sample volume Vx, standard concentration Cs, standard volume added Vs, concentration of ionic strength buffer Cse, ion charge n, Nernst factor (usually 0.0591) and potential of reference electrode Eo, into the table on the left. Measured voltages are shown below in the column labeled "voltages", both before (cell F17) and after (cell F18) the addition. The change in voltage deltaE is shown in cell G18, and the concentration calculated from the standard addition equation is shown in cell A22 (Click on this cell to display the equation in the entry bar at the top of the window). Compare the calculated value in cell A22 to the "correct" value Cx in cell B11. Note that the reference potential (Eo) has an effect on the measured voltages but no effect on deltaE nor on the calculated concentration. This calculated concentration won't be perfect, however, because adding the standard solution to the sample causes a slight increase in its ionic strength and thus a slight decrease in the activity coefficient of calcium. The percent difference between the calculated and true values of Cx is given in cell C22. You can reduce this error by using a smaller addition of standard (reduce Cs or Vx or both) or by using a greater concentration of NaCl ionic strength buffer (Cse, in cell B13). Using too much NaCl, however, will increase the interference of Na ions (c.f. the table of interference factors in rows 39-49). On the other hand, reducing the amount of standard added reduces deltaE and makes it harder to measure precicely. This effect can be simulated by specifying a voltage reading error in cell B14. The resulting % error in concentration is shown in cell E22, and the total error is shown in cell G22. For a given voltage reading error, is there a value of Vs that gives a minimum overall error? Is there an optimum concentration of NaCl ionic strength buffer (Cse, in cell B13)? Do these optima depend on the concentration of calcium in the unknown sample?  Geneva Geneva((|88,,x,, ~ y be(,, d'<~@ $%1 %