ELECTROCHEMICAL METHODS FOR DETERMINING SOLUBILITY PRODUCTS

ELECTROCHEMICAL METHODS FOR DETERMINING SOLUBILITY PRODUCTS

 Measuring electrode potentials is a good method for determining solubility products because the measurement do not disturb the equilibria involved
This experiment describes the procedure for measuring the solubility products of some silver salts
Begin by preparing a saturated solution of silver chloride by adding 1 to 2 drops of 0.1m silver nitrate solution to approx 100cubic cm of 0.01M solution of potassium chloride.
To form a reference half cell; place a calomel electrode into a beaker containing saturated potassium chloride solution ensuring that the fret is completely immersed in the solution
Place the two beakers side by side and connect them using an ammonium nitrate salt bridge.
Immerse a clean sliver electrode in the solution to form the silver half cell
The two electrodes are connected to a digital voltmeter.
Gently agitate the solution.
If the electrode is fragile, use a magnetic stirrer.
When the reading on the digital voltmeter steadies, note the reading.
If the sign is negative, simply change over the terminals
But note the polarity of the cell, i.e. which electrode is connected to the positive terminal when entering the result in your lab book
Repeat the experiment adding 1 drop of 0.1m silver nitrate solution to 0.02, 0.05, 0.1 and 0.2M solutions of potassium chloride in the silver electrode beaker.
Remember to wash and dry the electrode and bridge between measurements and always to put the same end of the salt bridge in the silver solutions.
Carry out analytical experiments for other silver salts by replacing the potassium chloride in the silver electrode beaker by solutions of known concentrations of potassium bromide, iodide, and chromate.
Calculate the silver electrode potentials and obtain the solubility products as described in the lab script.