Investigating for Cations and Anions
In this experiment I will investigate what cations and anions are present in various compounds. This will include carrying out a qualitative analysis, because I need to find out what type of cations and anions are there and not quantitative analysis, which includes finding out how much of each element there is.
- Wear glasses
- Wear gloves
- Do not mix more than two solutions
- Only mix the solutions listed by the teacher
- Handle the chemicals with extreme care
- Put the chemical solutions into a test-tube which is resting on a test-tube holder
- Follow school lab safety procedures.
- Various chemicals.
- Test tubes.
- Boiling tubes.
- Test tube holder.
- Bench mat.
- I first copied the chemical solutions listed.
- I put on some gloves and safety glasses.
- I got a test-tube holder and placed five test-tubes in it.
- I added the test solutions Copper Chloride to the test-tube.
- To this I added a few drops of Sodium Hydroxide solution.
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After the few drops a pale blue precipitate of Copper Hydroxide appeared that indicated the presence of Cu ions.
- I then added the test solution Iron Chloride to the second test-tube.
- To this I added a few drops of Sodium Hydroxide.
- After that a brown precipitate of Iron Hydroxide appeared that indicated the presence of Fe ions.
- To the 3rd test-tube, I added the solution Sodium Hydrogen Carbonate and added Dilute Sodium Hydroxide.
- I quickly covered the test-tube with a delivery tube and put the end of it into another test-tube with limewater.
- The limewater turned a cloudy/milky colour which indicated that there was CO present.
- In the 4th test-tube, I poured the solution Copper Chloride into the test-tube.
- I added some Artificial Silver Nitrate solution.
- A white precipitate appeared that indicated that there was Cl present.
- For the last test-tube, I put some Copper Sulphate solution into the test-tube.
- I then added Artificial Barium Chloride solution.
- A white precipitate appeared that indicated that there were Sulphate ions present.
- I then recorded all of my results and repeated the entire experiment again to make sure everything was correctly done.
- I then repeated the entire experiment again, with limewater as the solution added, to get a negative result.
The problems I encountered while doing this experiment were:-
- I didn’t know what the difference was between cations and anions and I tested for the wrong things.
- When testing for the Carbonate ions, I didn’t add enough Dilute Acid and nothing happened.
I repeated it and added more Dilute Acid this time.
- While testing for the Chloride ions, a fellow student bumped into me and I accidentally dropped the test-tube onto the floor. I stained my trousers, but I got it out by soaking it in water.
- While doing the above experiment, I accidentally added a wrong solution and I didn’t get the result expected.
- A fellow student accidentally poured some dilute acid on my hand and it felt like I burned myself.
- I couldn’t measure the amounts accurately as we didn’t have measuring cylinders, because another class was using it for their experiment.
- The accuracy of this experiment wasn’t very high because we didn’t know the amount of solutions to use.
- If more time was available, I could have improved this technique by doing it over a few more times and at least got 4 positive and negative results. This would greatly increase the accuracy and reliability of this technique.
There are similar techniques used in the industry for example: when you find a new substance which is unknown, so that means that you need to check what elements there are present. This method could be automated and done on the computer but when it comes down to putting the substance to the test it needs to be done by hand.
You also need a variety of scales so you can check that the result is the same. For example: you can use more substance and add a little bit of solution, you can use a little bit of the substance and add a lot of solution or you can put the substance to the test by adding different types of solution.
When doing these tests you need to use safety rules just like in any other lab, but because you are working with chemicals you need to make sure you got clear space to work on, that you wear goggles and a lab coat and that you do not spill any of these chemicals because you could have dangerous outcomes to it.