Ion Tests Laboratory Write-up

Data Table 3: Reactions of unknown solutions when specific compound solutions (used as indicators) are added. 

*Test not performed because of time restrictions, therefore results still remain unknown.

Conclusion:

Anions

Carbonate – When aqueous sodium carbonate reacts with dilute nitric acid the liquid effervesces. CO32-, NO3-, and Ca2+ are the ions involved in this reaction.

Sulfate – When aqueous sodium sulfate reacts with aqueous barium chloride a white cloudy white precipitate is formed. Na+, SO42, Ba2+, and Cl- are the ions involved in the reaction. Barium Sulphate was the precipitate.

Chloride – When aqueous sodium chloride reacts with aqueous silver nitrate a milky white thoroughly suspended precipitate is formed. Also, if the mixture is left in the sunlight there is a color change to lilac. Sodium, chlorine, silver, and nitrate ions are present in this reaction. The precipitates formed are sodium nitrate and silver chloride.

Iodide – When aqueous potassium iodide reacts with aqueous silver nitrate a color change to milky yellow takes place and milky precipitate is formed. Potassium, iodide, silver, and nitrate ions are present in this reaction. The precipitates formed are potassium nitrate and silver iodide.

Bromide – When aqueous sodium bromide reacts with aqueous silver nitrate a milky white precipitate is formed. Sodium, bromine, silver, and nitrate are the ions present in this reaction. The precipitate is silver bromide.

Cations

        

Aluminum – When aqueous aluminum hydroxide reacts with aqueous sodium hydroxide a cloudy rosy white precipitate is formed. Sulphate, sodium, and hydroxide ions are present in this reaction. The precipitate formed is iron hydroxide.

Zinc – When aqueous zinc sulfate reacts with aqueous sodium hydroxide a white precipitate is formed. Iron, sulphate, sodium, and hydroxide are the ions present in this reaction. The precipitate formed is zinc hydroxide.

Iron(II) – When aqueous iron sulphate reacts with aqueous sodium hydroxide a color change to mossy green occurs while the heavy precipitate formed gathers at the bottom. Iron, sulphate, sodium, and hydroxide are the ions present in this reaction. The precipitate formed is iron hydroxide.

Iron(III) – When aqueous iron chloride reacts with aqueous potassium thiocyanate a color change to orange takes place. Iron, chlorine, sodium, and hydroxide are the ions present in this reaction. The precipitate formed is iron hydroxide.

Iron(III) – When aqueous iron chloride reacts with aqueous sodium hydroxide a color change to stark red takes place. Iron, chlorine, and potassium are the ions present in this reaction. The precipitate formed is iron throcyacate.

Copper – When aqueous copper sulphate reacts with sodium hydroxide a dark blue precipitate is formed. Copper, sulphate, sodium, and hydroxide are the ions present in this reaction. The precipitate formed is copper hydroxide.

Unknown Solutions

        Analyzing the data above, we can conclude the following: Unknown solution C is copper sulfate and unknown solution D is potassium iodide. However, from the data above unknown solutions A, B, and E are rather undeterminable. Unknown solution C is mostly likely copper sulfate because from data table 2, it is seen that a “dark blue precipitate is formed” when copper sulfate reacts with sodium hydroxide – which is what resulted when sodium hydroxide was added to unknown solution C. Unknown solution D is mostly likely potassium iodide because from data table 1, it is seen that a “color change to milky light yellow” occurs when potassium iodide reacts with silver nitrate – which is what resulted when silver nitrate was added to unknown solution D. Unknown solution A seems not to be an ionic compound since it did not react with any of the ion testers. Unknown solution B and E are difficult to determine because several cations and anions in data tables 1 and 2 form white precipitates when sodium hydroxide or silver nitrate is added to them. From the information available, Unknown solutions B and E could be deduced as one of the following: sodium sulphate, sodium chloride, sodium bromide, aluminum hydroxide, or zinc sulfate.

Evaluation:

        This lab can be improved by the following: replacing the damaged droppers used for the unknown solutions, situating the chemicals closer to each other rather than in far apart in different places in the room, using several test tubes rather than one for all the tests, allotting more time to perform the lab. The droppers should be replaced because they have holes in them and are not perfectly useful in that condition. Secondly, it would be more convenient if the solutions were placed on one or two tables near each other rather several meters away from each other which causes the hassle of having to walk back and forth the room, maneuvering through desks, to do a new test each time. Relatively, part of the inconvenience was having to pour out the content of the single test tube over and over for it to be used for the next test and having to go back and forth the room to each time. It would have been better if a rack of test tubes was supplied so that the experimenter wouldn’t have to keep pouring out each mixture to perform a new test. Aside from that, the time necessary in performing this experiment because of the way it had been set up is long. However, the time available was short and so it was not possible for the experiment to be carried out completely, (as is seen in the data gathering section of this lab report). Yet most of the shortcomings this experiment is understandably due to the fact that there are many students in the class – therefore crowding up would take place if all the solutions were place on one table, and there are possibly not that many test tubes available for each student to have a set of, and the class period is only for a set amount of time; we cannot extend it freely to accommodate our purposes.