Solutions of NiSO4(aq), Al2 (SO4)3 (aq),
CoSO4 , and SnSO4 (aq) are in bottles labelled A, B, C, and D.
a) Design an experiment to identify which ionicsulfate solution is in which bottle. Give a list of
equipment and chemicals required. Describe
a step-by-step procedure for conducting the experiment
b) Explain why an activity series is required to identify each unknown substance
a) To identify which ionic sulfate solution is in each bottle, you can perform a series of precipitation reactions. Here is a step-by-step procedure for conducting the experiment:
1. Equipment and Chemicals Required:
- Test tubes
- Test tube rack
- Dropper or pipette
- Distilled water
- Sodium chloride (NaCl) solution
- Silver nitrate (AgNO3) solution
- Barium chloride (BaCl2) solution
- Hydrochloric acid (HCl) or sulfuric acid (H2SO4)
- Safety goggles and gloves
2. Label the test tubes A, B, C, and D to match the bottles.
3. Take a small amount, around 1-2 mL, of the solution from bottle A, and transfer it to the corresponding labeled test tube.
4. Perform the following tests using the procedure below:
i) Test for Chloride (Cl-) ions:
a. Add a few drops of silver nitrate (AgNO3) solution to the test tube containing solution A.
b. Observe if a white precipitate forms. If a white precipitate forms, it indicates the presence of chloride ions (likely Al2(SO4)3).
ii) Test for Sulfate (SO4^2-) ions:
a. Add a few drops of barium chloride (BaCl2) solution to the test tube containing solution A.
b. Observe if a white precipitate forms. If a white precipitate forms, it indicates the presence of sulfate ions (likely BaSO4).
5. Repeat steps 3 and 4 for bottles B, C, and D.
6. Once all the tests are performed, compare the results obtained for each bottle with the expected outcomes to identify which solution is in which bottle.
b) An activity series is required to identify each unknown substance because different metal ions have different activity levels or reactivity. The activity series provides a ranking of metals from most reactive to least reactive. This information is crucial when performing certain reactions, including precipitation reactions.
For example, in the precipitation reaction between a metal sulfate solution and a chloride solution, two possible reactions occur: metal sulfate + chloride → metal chloride + sulfate. The reaction only proceeds if the metal ion in the sulfate solution is more reactive than the metal ion in the chloride solution. If the metal ion in the chloride solution is more reactive, then no solid precipitate will form.
By referencing the activity series, you can determine which metal ions are more reactive than others and predict the outcome of specific reactions. This knowledge helps identify the unknown substance based on the observations made during the experimental procedure.
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I recommend color for Ni. The Al and Sn are colorless while most Ni solutions are green or blue. Co solutions are pink to blue. Remember that Al is amphoteric; i.e., it forms a white gelatinous ppt with NaOH which dissolves in an excess.
Ni forms a hydroxide also but it isn't colorless and doesn't dissolve in an excess of NaOH. Be careful, Sn is white and can be dissolved in an excess.