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Unformatted text preview: MAPUA I NST I TUTE OF TECHNOLOGY School of Chemical Engineering, Chemistry, Biological Engineering, and Material Science and Engineering Physical Chemistry Laboratory 2 - 3 rd Quarter SY 2010-2011 Neil Patrick P. Tangara , 3 rd Year B.S. Chemical Engineering Experiment No. 2 CONDUCT I M ETRY: DETERM I NAT ION OF T HE ELECTR ICAL PROPERT IES OF SOLUT IONS Austria, Meynard 1 , Tangara, Neil Patrick, Pudolin, Darlene, Santos, Emily Rose, Tan, Aeiocellis, Talingting, Creza Loraine 2 1 Professor; 2 Students, all from CHM171L/A31, School of Chemical Engineering, Chemistry, Biological Engineering & Material Science and Engineering, Mapua Institute of Technology ABSTRACT This experiment intends to determine the conductance of solutions and infer from it the relative mobility of monovalent ions. It also intends to determine the dissociation constant of a weak electrolyte such as Ammonium Hydroxide. The conductances of solutions of different concentrations were determined using the conductivity meter. For strong electrolytes, conductance was found to vary directly with concentration while for weak electrolytes; conductance had an inverse relationship with concentration. This report will discuss why such a phenomenon occurs. Keywords : conductivity meter, relative mobility, conductance, monovalent ions, dissociation constant, strong and weak electrolytes. I N TRODUCT ION In a given conductance cell, the conductance of a solution will depend on (1) the number of ions present and (2) the speed of these ions under a given voltage drop across the electrodes. The number of ions present will depend upon the strength (weak or strong electrolytes) and the concentration of the electrolyte. Strong electrolytes such as NaCl and HCl show greater conductance at a given concentration as compared to weak electrolytes such as NaC 2 H 3 O 2 and NH 4 Cl. Examination of the equivalent conductance of acetic acid and ammonia at different concentration shows the effect of dilution on the equivalent conductance, hence on the degree of dissociation. If an electrolyte is diluted sufficiently, it will finally reach a state of complete dissociation. The weaker the electrolyte, of course, the greater the dilution is required....
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