Chemistry Practical for Halide Ions

Introduction I will be carrying out two main tests- one of things I will be testing for is halide ions that may be present in solid salts. I will do this by adding sulphuric acid to the solid and then measuring the gases released- if either chlorine or uorine is present then an acidic fume will be produced and this can be measured by using universal indicator paper which will turn towards the red end of the spectrum. Moreover, if bromine is present then there will also be brown bromine vapour being produced, whilst iodine will evolve a purple vapour as well as fumes of hydrogen iodide. This test will be carried out in a fume cupboard as a safety precaution. My other test will be for halide ions in a solution rather than a solid and this consists of a two-step process. Firstly, an amount of the solid substance that is going to be tested will be dissolved in a solution and then this solution is going to be mixed with nitric acid to remove any unwanted ions that may interfere with the test. Then, silver nitrate will be added to the solution- if i f the solution remains clear then uorine is present- if the solution forms a white precipitate then chlorine is present- if the solution forms f orms a pale cream precipitate then bromine is present- if iodine is present then a pale yellow precipitate will form. It may be dicult to accurately di!erentiate between coloured solutions produced so another test is carried out to con"rm the potential halide present. In this test ammonia solution is added to the solution at di!erent concentrations. #hloride ions will dissolve in a wea$ concentration of ammonia solution, whilst Iodide ions are insoluble in any concentration of ammonia a mmonia solution %so a solid precipitate will remain& and bromide ions will only dissolve in concentrated ammonia solution Method  Test  Test for halide ions in solution '. Measure Measure 'ml of the un$nown un$nown solution solution using using a pipette pipette and then then transfer transfer this into a test tube (. Measure Measure 'ml of dilute dilute nitric acid acid %).*M %).*M &and then then transfer transfer this into into the same same test tube containing the un$nown solution +. dd ') drops drops of silver silver nitrate nitrate solution solution %).)*M& %).)*M& using using a teat pipette pipette to the the un$nown solution . ecord ecord results results / if the solution solution contained contained any any uoride uoride then no precipitat precipitate e will form0 if the solution contains any chloride then a white precipitate will form0 if  the solution contains any bromide then a cream precipitate will form0 if the solution contains any iodide then a yellow precipitate will form *. To con"rm con"rm the halide present present add 'ml 'ml of dilute ammonia ammonia solution solution %).*M& %).*M& %measure using pipette& and record observations- if chloride ions are present then the precipitate will dissolve and the solution will become clear 1. If the solution solution has has not became became clear then then add 'ml of concent concentrated rated ammonia ammonia solution %'M& %measure using pipette& and record record observations- if bromide ions are present then the precipitate will dissolve, but if the solution still contains the precipitate then iodide ions are present

2. epeat this ( more times and record results, then decided which halide is present  Test for halide ions in a solid '. 3et up fume cupboard and carry out experiment inside of it (. Measure *g of the un$nown mass using a weighting scale and spatulacontain the measured solid within a dry test tube +. dd * ml of sulphuric acid %'M& with caution and a gas will be released . Test the gas released using universal indicator paper which will turn towards the red end of the colour spectrum if an acidic gas is evolved which indicates that chloride ions were present *. epeat the experiment %steps ',( and +&and test the gas with "lter paper that has been soa$ed in potassium dichromate which will turn from orange to green if sulphur dioxide is present- in which case either bromide or iodide ions were present 1. Finally, repeat the experiment %steps ',( and +& and test the gas released by feeding it through a pipe into a * ml solution of lead nitrate %'M&0 if the solution turns cloudy then potassium iodide was present. 45uipment                 

6ilute 7itric cid %).*M& 3ulphuric cid 3olution %'M& 6ilute mmonia 3olution %).*M& #oncentrated mmonia 3olution %'M& 8n$nown halide solution 8n$nown potassium-halide containing mass 9ead 7itrate %'M& :otassium 6ichromate 3oa$ed :aper 3ilver 7itrate 3olution %).)*M& mmonia 3olution 8niversal Indictor :aper  Test Tube 3patula 6igital ;eighing 3cale Fume #upboard  Teat :ipette
is$ ssessment is$ 7itric cid- corrosive

:recaution The acid will be dilute so it will not be as ha=ardous as sulphuric acid- however I will ma$e sure that I am careful when using the nitric acid by ma$ing sure that he acid is securely contained

In event of occurrence Immediately rinse hands with cold water to dilute the acid>silver nitrate so it has less potential to cause harm to the region contacted. lso, I will use a fume cupboard to ma$e sure all the gases

3ulphuric cid- very corrosive>toxic

3ilver 7itrate- irritant> strong oxidiser #oncentrated mmonia 3olution- corrosive> toxic

and be caution when transferring it to solutions ;ill violently react with water, so I will ensure that the test tubes that are uses to contain the acid are dry0 also, I will use a fume cupboard to ma$e sure all the gases produced are contained I will be careful when handling the solution and transferring it I will ma$e sure that I wear eye protection when using the solution, so my eyes are protected from contact

produced are contained