anyone kknw the test for ions (gcse chemistry) :)

  • 0 votes


Posted Thu 26th April, 2012 @ 19:13 by Zeen
Edited by Zeen on Thu 26th April, 2012 @ 19:14

1 Answer

  • 1 vote

Hi Isit C3 you're talking about?
If so the test for positive ions is..

The Flame Test; 
Sodium- Golden Yellow
Lithium- Bright Red
Calcium- Brick Red
Barium- Green
Magnesium- Colourless
Potassium- Liac

You can also add NaOH (Sodium Hydroxide) To metals to make WHITE Precipitate..
Aluminum- Makes White Precipitate but you can add MORE NaOH to it and the metal will dissolve in the solution.
Magnesium and Calcium can be distinguished with the flame colours they produce.

Some Transitional metals form coloured precipates;
Copper (2+)-Light Blue
Iron (2+)-Dirty Green
Iron (3+)-Reddish-Brown 

You can add NaOH to Ammonia Ions to make Ammonia. You can detect Ammonia with Red Damp litmus paper which turns blue when the alkaline gas is present.

Testing for Negative Ions;
We can add Dilute Hydrochloric acid and Silver nitrate solution to the carbonate. It will fizz up and it will produce Co2 (Make the lime water cloudy)
HOWEVER if we heat 2 different Carbonates for example;
Zinc Carbonate; it will turn yellow when heated and then white when cooled (CO2 also produced)
Copper Carbonate (Turns black when heated, and CO2 given out.)

Halides (Halogens- Group 7)
We can add dilute Nitric acid and Silver Nitrate solution and 3 different coloured precipates will form.
Chlorine- White
Bromide- Cream
Iodide- Pale-Yellow

We can add Hydrochloric acid followed by Barium chloride. It will make a white precipitate followed by an insoluble salt called "Barium Sulfate." 

We can add NaOH to the substance and heat it, if no ammonia is detected we can add some Aluminium powder (ONLY a bit) ammonia gas will be produced and then the regular test for Ammonia is required. 

Answered Thu 26th April, 2012 @ 19:34 by Nishat Ahmed