1. Experiment 4 Observing Chemical Reactions Chemistry Department UCC1 st Year Practicals

2. Objectives Test your powers of observation Investigate the reaction of four inorganic chemicals with five common laboratory chemicals Devise a system for determination of the presence of these compounds in a mixture of unknown composition Apply this system to an unknown mixture containing two different metal salts

3. Experimental Four compounds: AgNO 3, Mg(NO 3 ) 2, Sr(NO 3 ) 2, Al(NO 3 ) 3 Five chemicals: HCl, H 2 SO 4, HNO 3, NH 3, NaOH You will react each laboratory chemical with each compound and record your observations Add all chemicals dropwise at all times

4. Table of Observations Reagent AgNO 3 Mg(NO 3 ) 2 Sr(NO 3 ) 2 Al(NO 3 ) 3 HCl H 2 SO 4 HNO 3 NH 3 NaOH

5. First test 0.5 mL of silver nitrate in a test tube and add 3 drops of HCl If you observe nothing then record this also A negative result is as important as a positive result

6. Second and third tests Repeat the first test using sulfuric acid, then nitric acid in place of hydrochloric acid Record your observations in the table Record any effervescence, colour change, precipitation

7. Fourth test Add NH 3 solution - a ppt may form Redissolves after more NH 3 added? If redissolves, add nitric acid until ppt reforms Keep adding nitric acid dropwise Does ppt redissolve again? Record all observations

8. Fifth test Add 1 drop of NaOH and wait for 30 seconds If reaction has occurred add NaOH If ppt redissolves add nitric acid until a ppt is formed Add more nitric acid, does ppt dissolve again?

9. Identifying unknown mixture Having performed all tests on all four compounds devise a method of identifying presence of one of the compounds in the unknown Firstly test the method on a solution of all four compounds Identify which two metal compounds are present in your unknown mixture A-F

10. Identifying unknown mixture Do all the steps of every test Note the letters of your unknown solutions in your write up Each unknown contains two metal salts Must identify both salts in the unknown

11. Report Include your table of observations Method of identification of metal ions in the unknown solution Brief discussion & conclusions Read Exp. 5 and Exp. 6a for next week