Chemistry - chemical analysis 17th March-28th April

Ratio between:

• distance travelled by solvent
• distance travelled by chemial

Rf = distance travelled by chemical / distance travelled by solvent

Always between 0 & 1

• Chcoclate powder > solute
• Hot water > solvent
• Final drink > solution

Mobile phase > water ......... Stationary phase > paper

Attracted to mobile phase = move quickly

• samples heated in flame
• enerdy provided excites electrons
• this makes them jump to higher energy levels
• when they fall back energy is released as light energy

Each metal ion absorbs & gives out its own characteristics pattern of radiation

Compared to data base to identify the metal ions & concentration of tem

Used so that water companies can detect if dangerous amounts of metal are present in water

• A formulation is a group of substances that don't react with eachother, however have desirable properties as a mixture
  • eg paints, varnishes, cosmetics, inks

• contains one substance
• molecules of elements, mixtures of compounds & mixtures of elements

Flame test

• Lithium (Li+) > crimson
• Sodium (Na+) > yellow
• Potassium (K+) > lilac
• Calcium (Ca2+) > red
• Barium (Ba2+) > green
• Magnesium (Mg2+) > no colour

Sodium hydroxide (coloured precipitates)

• Iron (Fe2+) > green precipitate
• Iron (Fe3+) > brown precipitate
• Copper (Cu2+) > blue precipitate

Sodium hydroxide (white precipitates)

• Calcium (Ca2+) > white precipitate (doesn't dissolve excess sodium hydroxide)
• Magnesium (Mg2+) > white precipitate (dosen't dissolve in excess sodium hydroxide)
• Alluminium (Al3+) > white precipitate (does dissolve in excecess sodium hydroxide)

Acid

• Carbonate ion (CO3 2-) > evervescence (fizzing)

Silver nitrate (after adding nitric acid)

• Chromide ion (Cl-) > white precipitate
• Bromide ion (Br-) > cream percipitate 
• Iodide ions (I-) > yellow precipitate

Barium chloride (after adding hydrochloric acid)

• Sulfate ion (SO4 2-) > white precipitate

Allotropes > different structures of the same element

3 types:

• graphite > soft & slippery, weak forces between layers
• diamond > hard, strong covelant bonds
• buckminster-fillerance

Carbon has a strong covelant bonds = high melting & boiling point

Only graphite can conduct electricity > de-localised sea of electrons

Diamond > 1 Carbon atom joins with 4 carbon atoms

Graphite > 1 carbon atom joins with 3 carbon atoms (not very strong)