Silver (Ag), Strontium (Sr), and Zinc  (Zn)

Silver (Ag), Strontium (Sr), and Zinc  (Zn)

By Kenna Chapman, Raeven Harris, and Greg Stephenson

 March 17, 2011

Abstract

The Separation of Ions lab was conducted for students to learn how to seperate three ions. In order to do this lab one must add sodium sulfate (Na2SO4)  to the test tube of solutions. The zinc (Zn2+) will precipitate out.  To obtain the precipitate from the solution, one needs to use a centrifuge. By adding sodium chloride (NaCl) to the solution the silver(Ag2+) should precipitate  out. The centrifuge should be used once again.

Then, one should add sodium sulfide (Na2S (aq) ) to the solution, allowing the strontium(Sr2+) to precipitate, and the centrifuge should be used one final time. The results of this experiment were the separation of all three ions and a clear, liquid solution left over. The conclusion is the experiment was a success. All three ions, Zn2+, Ag2+, and Sr2+ were separated using different solutions.

Lab Introduction

Purpose : The purpose of this lab will be to separate silver (Ag2+), strontium (Sr2+)and zinc (Zn2+) from a single solution when all three are combined into a test tube.

Procedure: Step 1

After one has received the ions in a single test tube, add 5 drops of Na2SO4 to the sample until the Zn2+ separates out in the form of zinc sulfate (ZnSO4)

Procedure: Step 2

The zinc sulfate can now be removed in to a test tube of its own. Put the tip of the funnel in to an empty test tube and lay filter paper on the top of the tunnel. The filter paper should allow the solution to pass through while not allowing the precipitate to filter. Remove the filter paper and slide the precipitate into an empty test tube.

What students actually did: To seperate the precipitate from the solution, they placed a test tube with water (same amount as solution) and the test tube of solution in a  centrifuge. It spun at high speeds and seperated the precipitate from solution.

Funnel/Filtration                Vs.                  Centrifuge

Procedure: Step 3      and            4

Add 5 drops of NaCl to the mixture of the remaining two ions. Keep adding until the Ag2+ begins to precipitate. The Ag2+ will precipitate and form silver chloride (AgCl2).

Put the silver chloride precipitate into a separate test tube by using the same centrifuge separation system as previously stated in step 2.

Procedure: Step 6      and            7

Add 5 drops of Na2S (aq) with the final ion, Sr2+, until it precipitates. It will form strontium sulfide (SrS).

It can now be taken out of the test tube and placed in its own. Use centrifuge separation as stated in step 2 with last empty test tube.

Procedure: Step 8

All three ions, or precipitates, should be in their own test tube.

See if the test tube with no precipitates burns red (meaning Sr2+ is still present) or green (meaning Zn2+ is still present).

Zinc                         Silver                      Strontium

Na2So4 NaCl Na2S

Before: The solution was clear, with no smell.

The solution alone was clear, liquid with water like qualities, no smell.

The solution alone had a horrible, sulfur, rotten eggs smell. The liquid was black and cloudy with grains that sunk to the bottom.

During: Once the drops were added, the substance began to appear cloudy and wavy.

The reaction caused a white fog to appear and sink to the bottom.

The reaction caused a bluish and fluffy appearance. The rest was clear. Still had pungent aroma.

After: The final precipitate was white, chalky and fluffy, almost snow like, rosy tint.

The final precipitate was white powder with some-what of a purplish tint.

The final product was a thin, wispy powder with a gray-black tint.

Ion Solution The solution was completely clear, with no smell

Observations

Analysis

The result of the experiment is the three precipitates in their own test tubes. Observations of the ions before, during, and after were recorded. Na2So4 before was cler with no smell, once added to the solution it became cloudy, the end result was a fluffy, chalky powder. NaCl before was a clear, liguid with no smell. Once it was added it became like a white cloud. After separated it settles as a purple-white powder. Na2S before it was added was a gray liquid with black grains at the bottom. It had a terrible, rotten-eggs smell. When put into the solution, it was blue and slightly fluffy. After the precipitate was separated, it was wispy, gray powder that smelled of sulfur.

Conclusion

    The lab was a success. All three ions were eventually separated from one another. The first time the lab was attempted, the filtration system failed to present efficient results. The filter paper only proved to absorb the solution, leaving hardly any left to continue the experiment. However, the second time, a centrifuge was used to spin the precipitate out from the rest of the solution. The last trial was completed without problems. A flame test was given, but the fire showed no results. The conclusion was made that the solution was too diluted with the other combined ions.