Chemical Kinetics

TITLE:
 POTENTIOMETRIC
 HALIDE
 TITRATION
 WITH
 Ag+ NAME: NATALIE BOWSINGH PROFESSOR: Dr Martin Telting Diaz CHEM: 241 SECTION WWW DATE: 03/07/2013

Introduction: The purpose of this experiment is to determine the quantity of KI and KCI in a supplied salt mixture. Mixture of halides will be titrated with AgNO3 solution and a ph meter is use for monitoring the mV and a analytical balance is used for weight.

Materials/ Apparatus: unknown containing KCI and KI , 6ml of 0.4 M bisulfate buffer, 1.2g AgNO3, pH meter with combination electrode and Ag wire electrode, magnetic stirrer, burette, pipette and volumetric flask

Procedure: To determine the quantity of KCI and KI in an unknown by performing a potentiometric halide titration with AgNO3 as the titrant.

1. The vial with the unknown was weighed, then poured into beaker, dissolved with 20ml of water and placed in a 100ml volumetric flask and further diluted to the fiducial mark. The empty vial was also weighed to get the unknown mass. 2. Then 1.2g of AgNO3 was weighed, placed in another 100ml volumetric flask and diluted to the fiducial mark. 25ml of the unknown was placed in 150ml beaker along with three drops of pH 2 bisulfate buffer and 50ml of the AgNO3 was placed in the burette as the titrant. The pH meter apparatus with combination electrode and Ag wire electrode was also placed in the beaker with the unknown solution and the mV was recorded. This titration was repeated again.

Discussion: The technique of potentiometric measures the potential of an indicator electrode that is coupled with a reference electrode. In this technique there is no current flow between the electrodes. The measured potential then can be used to determine the analytical quantity of interest, generally the concentration in some component in the analyte solution. The potential difference that develops in the electrochemical cell is the result of the free energy change that would occur if the chemical wre to...