仪器分析教学课件电子教案全套课件四.pptx

Conductometry (电导法);Conductometric Analysis;Conductometric Analysis;1.conductance(G) 、specific conductance (?) 、molar conductance(?m) 电导G：The resistance reciprocal is called conductance, its unit is Siemens G =1/R where 1S=1?-1 ; 电导率? : The resistivity reciprocal is specific conductance or electrolytic conductivity ? = G ? L / A its unit ：S ? cm-1 两电极板为单位面积，距离为单位长度时溶液的电导。;电导池常数θ：θ = L / A (A the surface area of electrodes; L the distance between electrodes) 由标准KCl溶液的电导率(查表)确定电导率和电导池常数;摩尔电导率(?m);Total conductance of the solution is directly proportional to the sum of the n individual ion contributions G = ?ci?m,i;无限稀释摩尔电导率 Molar conductance at infinite dilution is the characteristic constant for given electrolyte ;ions ?104 K+ 73.52 Na+ 50.11 Li+ 38.69 H+ 349.82 Ag+ 61.92 Cl- 76.34 Br- 78.4 OH- 198;3. Factors which influence conductance measurement;Electrodes Two parallel platinized Pt foil electrodes or Pt black with electrodeposited a porous Pt film which increases the surface area of the electrodes and further reduces faradaic polarization. 2.Primary standard solutions Primary standard KCl solution ,at 25℃, 7.419g of KCl in 1000g of solution has a specific conductivity of 0.01286Ω-1/cm. ;3. Conductivity Cell Avoid the change of temprature during determination 4. DC and AC Conductometry AC Conductometry can minimize the error caused by electrode polarization;1. conductometric titration电导滴定;acids and bases?titration curve ：;G = Kc;Conductivity of high purity water is about 5?10-8 S· cm-1 ;b. Determination of the total concentration of strong electrolyte solutions salinity of soil and sea water c. Determination of gaseous environmental contaminant in air eg. SO3 NO2, acidic rain determine the change of conductivity after absorption;Electroanalytic