Chemlab: Chemistry 3/5

Natural Salt Solutions 1: Ion Exchange


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Making an Ion Exchange Column
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Put a few mL of distilled water in a 10 mL graduated cylinder and note the water level.

Using a scoop or spatula, carefully transfer ion exchange resin to the cylinder.

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Add enough resin to make the water level rise by approximately 1.0 mL

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Swirl the graduated cylinder to put the resin into a slurry.

Quickly pour the slurry into the glass column.

Quantitative transfer of the resin is not necessary.
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The resin will settle into the bottom of the glass column.

Make sure the resin stays wet, either by flushing the column with water or eluant or by capping the bottom.

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A layer of sand is added to the top of the resin to keep in in place.

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The sand should be about 1/4 inch thick.

Charging a Column and Testing the Effluent
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Add eluant to the top of the column slowly and carefully, so as not to disturb the resin bed.

You can pour solution slowly down the side of the column opening or add solution dropwise, with a plastic dropper.

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Test the pH with indicator paper by taking a drop of effluent to piece of paper on a watch glass.

Acidic effluent can mean that cations are displacing protons on the ion exchange resin.

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To test for the presence of sulfate, bring a drop of effluent to a clean watch glass.

Then add a drop or two of Ba2+ solution.

Look closely for a cloudy precipitate of BaSO4.
Measuring the Height of the Blue Band of Cu2+
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The blue color of copper (II) ions is visible on the resin in the column.

Measure the height of the blue band and the total column height.

Prelab Problem 3
When 5 mL of 0.015 M CuSO4 solution is added to a column, a blue band measuring 1.0 cm forms. What is the capacity of this column, in milliequivalents, if the total column height is 5.0 cm? When the heights are measured, you estimate the values to the nearest 0.1 cm. What are the absolute and relative uncertainties of the total column height and the height of the blue band? Definitions of absolute and relative uncertainty are given in the section at the start of your lab manual manual called Computing Uncertainty in Laboratory Data and Results.

Saturating the Column with Na+

Add NaOH in small amounts and keep track of the volume of solution you add.

Monitor the pH of the effluent drops as you add NaOH to the column.

How will you know when the column is saturated? The slide show (left) may give you some clues.

How will you estimate the column capacity from this experiment?

Having trouble viewing the slideshow? Help is here.
Weighing samples of Potassium Hydrogen Phthalate
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Use the analytical balance to weigh three samples of KHP. Be sure to record an accurate mass for the sample in each labelled vial. Tape your vials together and label them with your name and lab section.

For more information, see the Techniques page on the Analytical Balance

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