T4 chemical changes
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what is oxidation/reduction
oxidation - when a substance gains oxygen reduction - when a substance loses oxygen
what are the trends in reactivities of metals in reactions with acids/water
metals above H2 in reactivity react with acid to produce H2, the more reactive the metal is, the quicker and more violent reaction with acid occurs metals below H2 don’t react with acid not all metals above H2 react with water - mostly group 1 and 2 metals aluminium is the borderline case
what is a displacement reaction
reaction where a more reactive metals displaces a less reactive metal from a compound
how are unreactive metals found in earth
in their natural state
how can metals less reactive than carbon be extracted
reduction with carbon carbon displaces the metal in a metal oxide - gets oxidised to carbon oxides metal from the metal oxide gets reduced to the pure metal
how are metals more reactive than carbon extracted
electrolysis
how are oxidation and reduction defined in terms of electron transfer
oxidation - loss of electrons reduction - gain of electrons
general equation for a reaction between metals and acids what type of reaction is this
metal + acid > salt + hydrogen redox reaction, also displacement reaction
which metals in the reactivity series will react with acid
those above hydrogen
general equation for a neutralisation reaction
base + acid > salt + water
general equation for the reaction between metal carbonate and acid
metal carbonate + acid > salt + water + carbon dioxide
general equation for the reaction between metal oxides and acids
metal oxide + acid > a salt + water
what is a redox reaction
reaction where both oxidation and reduction occurs
how is a soluble salt formed
• react the excess with some insoluble chemicals • filter off the leftovers • crystalise the product
what do acids and alkalis produce in aqueous solutions
acids - hydrogen ions alkalis - hydroxide ions
what are bases, acids and alkalis
b - compounds that neutralise acids acids - produce hydrogen ions in aqueous solutions alkalis - soluble bases which produce hydroxide ions in aqueous solutions
what is the pH scale and what does a pH of 7 show
measure of acidity/alkalinity of a solution neutral solution
state the general equation for a neutralisation reaction in a short, ionic form
H+ + OH- > H2O
what is a strong acid and a weak acid
S - completely ionised in aqueous solution w - only partially ionised in aqueous solution
what happens to pH as concentration of H+ increases
decreases
what is a concentrated acid and what is a dilute acid is this the same as a strong and weak acid
c - has more moles of acid per unit volume than dilute d - refers to solutions of low concentration not the same - concentration is different to strength of an acid strength refers to whether the acid is completely ionised in water (strong) or only partially (weak)
as the pH is decreased by one unit, what change is seen in the hydrogen ion concentration
increases by a factor of 10
what is electrolysis
passing of an electric current through ionic substances that are molten or in solution to break them down into elements ions are discharged at electrodes to produce these
what is an electrolyte
liquid/solution which conducts electricity