SKILL: Planning and Designing
OBSERVATIONS: A student is given a small beaker containing an unknown salt, x. The salt is crystalline, deliquescent and colorless. The student is asked to perform test and observation on the salt to determine the cation and anion present.
HYPOTHESIS: Perhaps by using the flame test or reacting salt x with NaOH, or NH4OH the cation could be distinguished by observing the color changes or solubility while reacting salt x with H2SO4 or a mixture of copper turnings and concentrated sulphuric acid the anion of the salt could be found.
AIM: To determine the constituents of salt x.
* Salt x
* Concentrated hydrochloric acid
* Concentrated sulphuric acid
* Platinum wire
* Bunsen burner
* 2 test tubes
* Universal pH paper
* 4 Droppers
* Dilute sodium hydroxide
* Ammonium hydroxide (ammonium solution)
* Copper turnings
* Ammonium salt (NH4Cl)
* Alkali (Ca[OH]2)
1.) Moisten a small amount of the solid with concentrated hydrochloric acid and dip a piece of platinum wire into the mixture and heat strongly in a Bunsen’s flame. 2.) Observe and record the color of the flame produced.
3.) If no color changes during the flame test then place an adequate amount of salt x in a test tube and prepare a solution of it by adding water. 4.) Using the dropper, add 10 drops of dilute NaOH solution to the solution of the sample and look for a precipitate. 5.) Add excess NaOH solution and look for the precipitate re-dissolving. 6.) If no precipitate is formed, heat the test tube gently over a Bunsen’s flame and test for Ammonia by using a universal pH paper 7.) Record relevant observations.
8.) If the precipitate is white in color and is soluble in excess NaOH then carry out procedure 9. 9.) Repeat procedures 3 to 7 with NH4OH and record relevant observations. 10.) To test for the cation Observe and record...
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