Chemical Change Flashcards
what are wide range indicators
contain a mixture of dyes that gradually change colour over a range of ph
how are ph probes used
probe attached to meter and probe in solution you are measuring. more arcuate as you get a number
what happens if you dissolve an acid in water
hydrogen ions will be formed (H+)
what happens to alkali if you dissolve it in water
hydroxide ions form (OH-)
what is the general formula for a neutralisation reaction
acid + alkali = salt + water
during neutralization reactions hydrogen ions and hydroxide ions react to form what
water
what is a titration
an experiment that lets you see what volume of reactant is needed to completely react with another reactant
what is universal indicator
used to estimate ph of solution. thr colour gradually changes. cantuse in titration cus colour change is too gradual
what indicators could be used in a titration and why
phenolphthalein, methyl orange and litmus
they are single indicators meaning they have one distinct colour change
what is the colour change in phenolphthalein
pink in alkalis colourless in acid
what is the colour change in methyl orange
yellow in alkalis red in acids
what is the colour change in litmus
blue in alkalis red in acids
what does the strength of an acid tell you
the proportion of acid particles that will dissociate to produce H+ ions in a solution. high proportion = high strength
why are strong acids more reactive than weak acids
reactions of acids involve H+ ions reacting w other substances so if the concentration of H+ ions is higher then the rate of reaction will be faster
what is the relation between the ph scale and the concentration of H+ ions
for every decrease of 1 the concentration of h+ ions increase by a factor of 10
how does concentration effect the ph of an acid
if the acid has been watered down then the amount of h+ ions will be proportionally smaller so the ph will increase even though the acid maybe a strong acid
what are bases
substances that can react with acids in neutralization reactions. all metal oxides and hydroxides are bases
why are soluble metal hydroxides alkalis
disolve in water to produce OH- ions
what is the general equation for the reaction of metal oxides or metal hydroxides with acids
they make salt and water
hydrochloric acid + copper oxide =
copper chloride + water
what do reactions with hydrochloric acid, sulphic acid and nitric acid give in the name
chlorides
sulphates
nitrates
list the reactivity series
potassium sodium lithium calcium mafnesuim carbon zinc iron hydrogen copper
how can you test the reactivity of metals
measure temp change in reaction
react w metal and monitor rate of hydrogen produced
acid + metal =
salt and hydrogen
how can hydrogen be detected
lit splint in mouth of tube . makes squeaky pop
metal + water =
metal hydroxide + hydrogen
what is a metal ore
rock containing enough of the metal to make it profitable to extract
what is oxidation
gain of oxygen.
what is reduction
loss of oxygen
how are metals less reactive than carbon extracted from their ores
reducing it n a reaction with carbon. Oxygen is removed from ore and the carbon gains it so the carbon is oxidized. displacement.
how are metals more reactive than carbon extracted from their ores
electrolysis
what is a redox reaction
oxidation and reduction occurs at the same time
what happens in terms of electrons in oxidation and reduction
oxidation - loss of electrons
reduction - gain of electrons
why are displacement reactions redox
metal ion is being reduced and metal atom is being oxidised
what is an electrolyte
liquid in electrolysis that conducts electricity. They contain free ionns and are usally a molton or disolved ionic substance
e.g sodium chloride
what is an electrode
solid that conducts electricity that is submerged in electrolyte. ions move from one elecrode to the other which is what compleates the circuit
where do the positive ions more to in electrolysis
cathode (negative electrode) and gain electrons
where do the negative ions move to in electrolysis
the anode (positive electrode) and lose electrons
what happens after an ion gains or losses electrons in electrolysis
becomes atom or molecule and is released
what are binary compounds
ionic compounds containing two elements that are ions - a positive metal ion and a negative metal non ion
what do half equations show in electrolysis
show the reactions at the electrodes
how do you draw a half equation for electrolysis
on the left hand side of the equation, draw the symbol for the positive ion
write the symbol for the neutral molecule on the right hand side of the equation
balance number of atoms in the equation
balence the charges by adding or subtacting electons shown as e-
this works for at the cathode. for writing one forthe anode , the negitive ion needs to be on the right hand side
what can bauxite be purified to make
aluminium oxide (Al2O3)
is is aluminon oxide dissolved in molten cryolite
brings melting point from 200 to 900
what material could be used as an electrode
carbon (graphite)
in the electrolysis of aluminon oxide, why do the electrodes have to be sometimes replaced
oxygen loses electrons at positive electrode making neutral O2 whick react w the carbon and form co2
at the negative electrode what would happen if a h+ ion and metal ion is present when the metal is more reactive than the hydrogen
the more reactive element is more likely to stay as an ion so hydrogen will be produced and the metal will remain as an ion
if OH- is at the positive electrode but not any halide ions what will happen
OH- ions are discharged and oxygen and water will be formed
