chemical changes

• lower pH= acid
• higher pH=alkaline
• acids and bases neutralise each other
• alkalis form OH- ions in water
• acids are h+ ions
• acid +base -> salt + water
• titrations are used to find out concentrations
• litmus- blue in alkalis and red in acids
• phenolphthalein- pink in alkalis and colourless in acids
• methyl orange- yellow in alkalis and red in acids
• strong acids- H2SO4, HCl, HNO3
• weak acids- ehanoic, citric, carbonic acids
• strong acids- all particles dissociate to release H+ ions
• weak acids- only a small proportion of particles dissociate to release H+ ions
• ionisation of weak is a reversible reaction
• some metal oxides and metal hydroxides dissolve in water to form a solution (alkalis)
• even bases that dont dissolve in water will still take part in neutralisation reactions with acids
• metal oxides and metal hydroxides react with acid to form a salt and water
• acids and metal carbonates produce carbon dioxide
• metal carbonates react with acids to form salt, water and carbon dioxide
• copper oxide + hydrochloric acid= copper chloride
• reactivity series- group order= 1,2,3,TM,4,TM
• when metals react with water or acid, they lose electrons to form positive ions
• some metals react with acids to form a salt and hydrogen gas
• metal + water -> metal hydroxide + hydrogen
• formation of metal ore: rocks are heated and oxidised to produce metal oxides
• oxidation =loss of electrons or gain of oxygen
• extraction of metal: reduction of metal oxides with carbon or electrolysis
• reduction= gain of electrons or loss of oxygen
• some metals can be extracted by reduction with carbon
• metals higher than carbon in the reactivity series have to be extracted using electrolysis
• metals below carbon in the reactivity series can be extracted by reduction using carbon
• reduction using carbon- iron oxide is reduced in a blast furnace to make iron
• if elements are transferred, its a redox reaction
• reduction and oxidation happen at the same time in redox reactions
• iron atoms are oxidised to Fe2+ ions when they react with a dilute acid: Fe + 2H+ ->Fe2+ + H2
• displacement reactions are redox reactions
• displacement reaction rule: a more reactive metal will displace a less reactive metal from its compound
• in displacement reactions, it's always the metal ion that gains electrons and is reduced. The metal atom always loses electrons and is oxidised
• electrolysis uses an electric current to break down a compound into its elements