chemical changes
Cards (10)
- acids and bases
- ph scale is measure of how acidic or alkaline something is
- indicator is a dye that changes colours due to ph
- ph probe gives you a number due to its ph
- acid + base = salt + water
- H+ + OH- = H2O
- tittrations
- exactly how much acid is needed to neutralise alkali
- using pipette and filter add set volume of alkali to conical flask with indicator
- fill burette with acid of known concentration , record initial volume
- add acid to alkali bit by bit , give flask regular swirl
- indicator changes colour when all alkali neutralised
- record final volume of acid
- single indicators
- blue in alkali red in acid = litmus
- pink in alkali colourless in acids = phenolphthalein
- yellow in alkali red in acids = methyl orange
- strong and weak acids
- strong acids ionise completely in water and release all H= ions
- weak acids do not fully ionise in water and release some H+ ions , reaction reversible
- ph of acid or alkali is measure of concentration of H+
- reaction of acids
- acid + metal oxide = salt + water
- acid + metal hydroxide = salt + water
- acid + metal carbonate = salt + water carbon dioxide
- making soluble salts with insoluble base
- gently warm acid with bunsen burner
- add insoluble base to acid until in excess
- filter out excess solid in solution
- pure , solid srcytals heat using water bath
- reactivity series
- potassium
- sodium|
- lithium
- calcium
- magnesium
- carbon
- zinc
- iron
- tin
- lead
- hydrogen
- copper
- silver
- gold
- acid + metal = salt + hydrogen
- metal + water = metal hydroxide + hydrogen
- separating metals from metal oxides
- formation of metal ore = oxidation
- extraction of metal = reduction
- any metal below carbon in reactivity series can be reduced by carbon
- redox reactions
- electrons transferred , its redox
- displacements reactions
- electrolysis
- positive ions in electrolyte move towards cathode and gain electrons vice versa
- creates flow of charge
- ionic solid cant be reducded because ion can move freely
- metals extracted from ores
- aluminium extracted from bauxite
- aluminium oxide has high melting so mixed with cryolite
- molten mixture contain free ions
- positive al3+ attracted to cathode turn into neutral atoms sink
- negative o2attracted to anode turn to neutral oxygen , combine to form O2 molecules
- electrolysis of aqueous solutions
- hydrogen ions (H+) and hydroxide ion (OH-)
- cathode = hydrogen ions if metal ions more reactive
- anode = halide ions present they are produced in not OH- ions