Qualitative-Tells you what is present, detects poison etc
Quantitative-Tells you how much is present, used in alcohol test
Qualitative-Can test mysterious substances, such as Ionic substances, so it helps to find out the different substances because of the Ions.
Tests for Postive Ions
- Sodium Na+- ORANGE
- Potassium K+-LILAC
- Calcium Ca2+-RED
- Copper Cu2+-Blue/Green
Calcium + Sodium Hydroxide = White Precipitate
Copper(II) + Sodium Hydroxide = Blue Precipitate
Iron(II) + Sodium Hydroxide = Green Precipitate
Iron(III) + Sodium Hydroxide= Reddish Brown Precipitate
Aluminium + Sodium Hydroxide = White at first then colourless
Ammonium + Sodium Hydroxide = None, pungent smell given off
Tests for Negative Ions
Negative Ion test:
Carbonate + Hydrochloric Acid= Carbon Dioxide and Water, the Carbon Dioxide can be tested by using limewater, which turns milky when CO2 is present.
Sulphites + Hydrochloric Acid= Sulphur Dioxide and Water, SO2 can be tested by using damp Potassium Dichromate(VI) Paper, which turns orange to green when SO2 is present.
Barium Chloride + Sulphate= Barium Sulphate Which is White, HCL is added before the test to remove any Sulphite or carbonate Ions.
Halides Test: Nitric Acid + Halide + Silver Nitrate
Chloride= White Precipitate Silver Chloride
Bromide= Cream Silver Bromide Iodide= Yellow Silver Iodide
Acid & Alkalis
Litmus: Blue turns Red when H+ is present (ACID)
Red turns Blue when OH- is present (ALKALI)
Phenolphthalein: Pink In Alkali, Colourless in Acid
Methyl Orange: Yellow in Alkali, Red in Acid
Universal Indicator- Used to estimate pH
Acid + Metal= Hydrogen Gas- Squeaky pop is used to detect Hydrogen which tells us that Acid is present
Ammonium Salt+ Hydroxides= Ammonia Gas which is smelly and can be tested by using universal indicator, which turns Purple
Moles= 6.023 x 10^23 ( Power 23)
One mole of any atom or molecule= mass in grams of the relative formula mass such as Carbon which has 12 relative mass, so 1 mole is 12g
Number of moles= Mass in g/ relative formula mass
One mole of any gas always takes 24 dm3 or 24 00cm3 at room temperature and pressure or 25C and 1 Atmosphere.
Volume of gas= Mass of gas/ relative formula mass x 24
To calculate the volume when you know the mass you do:
Find the reacting mass then convert the mass into a volume
Quantitative chemistry and solution
To find out how much something is dissolved by evaporating water:
Weigh a clean dry evaporating basin then put 10cm3 of the solution in the basin
Gently heat the basin
Weigh the the basin again then reheat and reweigh until the solution is finished
Mass Concentration= Mass (g)/ Volume (dm3)
Mole Concentration= Number of Moles/ Volume (dm3)
You can convert Mass concentration into Mole concentration by:
Mass Concentration (g/dm3)= Mole concentration (mol/dm3) x formula mass
Concentration of a solution doesn't always work because sometimes the solution evaporates with the water so Titration is used.
Titration allows you to find how much acid is needed to neutralise an alkali solution or vice versa.
You use a pipette and filter, then add some alkali to a conical flask with some indicator.
Next fill the burette with acid, has to be done below eye level. Then with the burette add some acid to alkali a bit at a time. Also give the conical flask a regular swirl.
When the indicator changes colour completely it means the alkali has been neutralised. Record the volume of acid used. Repeat it.
Water has to be from poisonous salts for drinking, it is filtered and chemicals are added to it to kill microbes. Also filtered to remove nasty tastes and smell.
Water is monitored constantly to ensure water is safe to drink.
Water is used as a solvent for most ionic compounds. It attracts the ions and the solid structure falls apart. Many covalent compounds don't dissolve in water.
It is essential for life. Used for many different things