Pre-Exam Panic.

A quick run through of tests for just about everything I need to know.

Simple place to start is flame tests.

You grab a powdered substance and burn it and see what colour it turns - here's the list...

Sodium - Yellow/Orange

Potassium - Purple

Calcium - Red

Magnesium - Really really bright.

Now, how to test for metals in compounds dissolved in water....

Zinc - you need to add sodium hydroxide drops IN EXCESS - White precipitate (which goes away in excess sodium hydroxide solution).

Copper(II) - add sodium hydroxide drops - Light blue precipitate

Iron(II) - add sodium hydroxide drops - Green precipitate (that eventually turns reddish brown)

Iron(III) - add sodium hydroxide drops - Reddish brown precipitate

Magnesium - add sodium hydroxide drops IN EXCESS - White precipitate (that's here to stay, regardless of excess sodium hydroxide solution).

Here's the equation for those lot ---

eg. Copper Sulphate + Sodium Hydroxide ---> Sodium Sulphate + Copper Hydroxide

CuSO4 + 2NaOH ---> Na2SO4 + Cu(OH)2

Now then, here comes the hard bit. First of all, these are tests for halide ions in water. We're technically testing for anions (the negative bit that conducts electricity or something... basically, the Surname of the chemical).

Chloride - add dilute nitric acid and silver nitrate solution - White precipitate

Bromide - add dilute nitric acid and silver nitrate solution - Creamy white precipitate

Iodide - add dilute nitric acid and silver nitrate - Yellow precipitate

Sulphate - add dilute hydrochloric acid and barium chloride solution - White precipitate

Nitrate - add sodium hydroxide to solution and warm it up, then add aluminium powder and test the gas produced - Red litmus turns blue (Ammonium produced)

Now, to identify anions in solids, we need to add either dilute hydrochloric acid or sulphuric acid to the solid, then pass any gas produced through limewater. If the water goes milky/cloudy, the solid is a carbonate.

There are two solid carbonates, and we can identify them because Copper(II) carbonate is a green solid which when heated goes black and gives of CO2.

Meanwhile, Zinc Carbonate is a white solid and goes yellow when heated and gives of CO2.

And finally, the easy tests on how to identify gases.

We all know that oxygen relights a burning splint, hydrogen produces a squeaky pop and carbon dioxide turns limewater milky. But I also need to know that chlorine chlorine turns damp blue litmus paper red then white. And I need to know that ammonia turns damp red litmus paper blue :)

Lurrrrrvley, I'm done for this evening.

Ciao Ciao!