Identification of ions (1 Viewer)

[gwc]

Hi, is it better to do precipitation tests first or do flame tests first? I'm guessing that it would be better to do precipitation tests first then check with flame tests if suitable, since the flame test for Iron nitrate and Lead nitrate are toxic, however I just want to check. also, how do you differentiate between Iron(II) and Iron (III)? Any help would be appreciated!

 

[SuperAltastic]

Identification of ions is a great dot point and easy marks if you know the procedure; the following procedure is the one I used to identify ions.

Cation Test:
0. Split solution into 2 equal portions.
1. In first portion Add HCL is ppt than it is lead to confirm add iodide should turn yellow.
2. If no ppt than filter and divide again into two portions, in one add h2so4 and it should form a white ppt = barium or calcium, to test you can do a flame test or to the portion divided after adding and filtering HCL you can add sodium fluoride it it turns white than it is calcium and then do a flame test to confirm.

3. In the second portion you divided initially add NaOH one of 3 results will occurs
- It will turn brown = Fe3+ to test add KSCN it will turn red.
or - It will turn green = Fe2+ to test add KMNO4 it should be colourless.
or - It will turn blue = Cu2+ to test add NH3 to dissolve it if it stays a deep blue than it is correct.

Anion Test:
1. Add HNO3- (nitric acid) if there is effervescence (bubbles) than carbonate ion is present.

2. If no bubbles than add barium nitrate if there is a precipitate (ppt) than it is sulfate you can test this by adding nitric acid to the solution if the ppt is still there then it is sulfate as sulfates are insoluble in ph<7.

3. If no ppt than add silver nitrate, if there is a ppt than it is chloride to test put in sunlight should turn purple.

4. If no ppt than add ammonia until the ph is 8 -10 than add barium nitrate, it should be a white ppt = phosphate to test add nitric acid it should dissolve as it is soluble in ph<7.

Finally always remember to filter if there is no ppt then do the next step.