Chemical changes Flashcards
what is oxidation/ reduction
oxidation- when a substance gains oxygen
reduction- when a substance loses oxygen
what is the reactivity series of metals
what are the trends in reactivities of metals in reactions with water/acids
. the series shows the metal in order of their reactivity
. metals above h2 in reactivity series react wid acid to produce h2. The quicker and more violent reaction with acid occurs.
. metals below h2 dont react with acids.
. Not all metals above h2 react with water- mostly group 1 and ii metals.
Aluminium is the borderline case
what is a displacement reaction
a reaction where a more reactive metal displaces a less reactive metal from a compound.
how are unreactive metals found in earth
in their natural state , as they are unreactive
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 oxides gets reduced to the pure metal.
how are metals more reactive than carbon be extracted
by electrolysis
what is the general equation for a reaction between metals and acids
what type of reaction is this
- metal add acid- salt add hydrogen
- redox reaction, also a displacement reaction
which metals in the reactivity series will react with acid
those above hydrogen
what is the general equation for a nuetralisation reaction
base add acid- salt add water
what is the general equation for the reaction between metal carbonate and acid
metal carbonate add acid - salt add water add carbon dioxide
what is the general equation for the reaction between metal oxides and acids
metal oxide add acid- a salt add water
how is a soluble salt formed
- react the excess acid with some insoluble chemical
- filter off the leftovers
- crystallise the product
what do acids and alkalis produce in aqeous solutions
.acids produce hydorgen ions
.alkalise produce hydroxide ions
what are bases,acids and alkalis
bases are compounds that nuetralise acids.
acids produce hydrogen ions in aquoes solutions
alkalis are soluble bases,produce hydroxide ions in aqueos solutions
what is the ph scale and what does the ph 7 show
. the measure of acidity/alkalinity of solution
. nuetral solution
state the general equation for a nuetralisation reaction in a short , ionic form
H plus add OH- = H20
name the following salts
.LiNO3
.K2CO3
.MgBr2
.BaSO4
- lithium nitrate
2.pottassium carbonate - magnesium bromide
- barium sulfate
what is electrolysis
the 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
the liquid/solution which conducts electricity
what is a cathode and what is an anode
. cathode is the negative electrode
.anose is the positive electrode
what occurs at the anode and what occurs at the cathode during electrolysis
. reduction occurs at the cathode
. oxidation occurs at the anode
. in aqueos electrolysis , which element is discharged at the cathode
.oxygen is produced at the anode unless what
. the less reactive element discharges at the cathode. Hydrogen is produced unless there is a less reactive metal, in which case the said metal is produced.
.oxygen is produced at the anode unless the solution contains halide ions, in which case halogen molecules are produced
how is aluminium manufactured
why is it expensive
. aluminium is made through the electrolysis of oxide and cryolite.
. lots of energy is needed to produce the current in electrolysis which makes this process expensive
what are the half equations in the extraction of aluminium
oxygen reacts with c of the anode producing CO2-carbon dioxide
why is cyrolite used in this process
it lowers the melting point of aluminium oxide, reducing energy costs
