C 5.1-5.8 chemical changes Flashcards
what is the reactivity series
a list of metals in order of their reactivity
how can you order metals
by comparing how they react with water or whit dilute acid
reaction with water of metals + order of reactivity
alkali metals react giving off hydrogen gas and leaving alkaline solutions, most metals don’t react
potassium
sodium
lithium
when do you use acids to show reactivity series
when reaction with water is too slow
how do we compare the reactivity of metals
by looking at how fast or violent their reaction with water and acids are
the speed of reaction with dilute acids is indicated by…,
rate at which bubbles of hydrogen are given off
when does a displacement reaction occur
when a more reactive element displaces a less reactive element from a compound
eg of displacemnt reaction
Mg + CuSO4=MGSO4+ Cu
what is an ionic equation (eg with Mg + CuSO4=MGSO4+ Cu)
shows only atom and ion that change in a reaction
Mg + Cu(2+)= mg (2+) + Cu
how can you give positions in the reactivity series to the non-metals hydrogen and carbon
on the basis of displacement reactions.
carbon can displace zinc from its oxide but not alumionium so in the series is placed in between them two.
copper can’t displace H from an acid whereas lead can so H is in between them
most of metals need to be
extracted from a compound
what do metals often need to be extracted from
oxides are the ores ,
created from reaction with oxygen
name of reaction that separates a metal from its oxide
reduction reaction
how does reactivity series help you in ores extraction
help you decide best way to extract the metal
what will carbon(non-metal) do to extract metals
will displace less reactive metals from their oxides
can only be used when carbon is more reactive
process and equation to extract metals with carbon
heat metal oxide with carbon, removing the hydrogen
metal oxide + carbon = metal + carbon dioxide
when is electrolysis used
to extract metals more reactive than metals
how and from what is aluminum extracted from compound (aluminum oxide)
electrolysis from bauxite
process of electrolysis with aluminum
aluminum oxide is mixed with molten cryolite to lower the very high melting point and reducing the energy needed. molten mixture contains free ions(conducts energy) positive ions of AL(3+) are attracted to the negative electrode where they each pick up 3 electrons and turn into neutral atoms. negative O(-2) ions are attracted to positive electrode where they each lose electrons, forming neutral oxygen that combine to form O2 molecules
when is salt formed (metal)
equation
reaction takes place between a metal and an acid, when hydrogen in an acid is wholly or partially replaced by metal or ammonium ions
metal + acid =salt+ hydrogen
why are alkali metals never added to acid
too reactive, dangerous
what kind of metals can react to form salt
metal must be above hydrogen in reactivity series but not too reactive
the salt you make depends on
metal you use
zinc metal will always make zinc salts
how can a sample of the salt make from reaction be crystalized
by evaporating off the water
what are bases
compounds that can neutralize acids (alaklis)
WHAT IS NEUTRALISATION
acid + base = salt + water
two reactions where you can make salts
solutions of an acid and an alkali
acid with carbonate
purpose of indicator
indicate if reaction is acid or alkaline
acids react with …. to form salts
metals, bases and carbonates
A soluble salt can be prepared by reacting an acid with a suitable insoluble reactant including:
a metal
a metal oxide
a metal hydroxide
a carbonate
process to get a soluble salt
Add powdered insoluble reactant to acid in a beaker, one spatula at a time, stirring to mix. Continue adding powder until it is in excess (some unreacted powder is left over). All the acid has now reacted.
Filter the mixture in the beaker to remove the excess solid. The filtrate now contains only the salt and water.
Heat the solution in an evaporating dish over a water bath. Stop heating when small crystals start to appear around the edge of the evaporating basin. The solution is now saturated.
Leave the saturated solution at room temperature for a day or two. This gives time for large crystals to form.
If necessary, dry the crystals by dabbing gently with filter paper.
what is an acid
substance that forms aqueous solutions with pH less than 7
what is a base
substance with pH greater than 7
metal oxides are bases
what do alkalis form in water
OH- ions
what do acids do in aqueous solution
they ionise, produce hydrogen ions
what happen to strong acids in water
ionise completely , all acids particles dissociate to realese H+ ions
what happen to weak acids in solution
do not fully ionise, only a small portion of particles dissociate to release H+ IONS
WHAT DOES THE IONISATION OF A weak acid set up
equilibrium between undissociated and dissociated acid, as it is a reversible reaction
equilibrium lies to the left as only a few H+ released
why are the strong aciuds more reactive on the same concentartion
concentration of H+ higher , rate if reaction faster
why is pH of strong acid always less than weak acid in same concentration
for every 1 on pH cale , concentration of H+ ions increase by a factor of 10
what is the concentration acids
how much acid in a certain volume of water
when will pH decrease(concentartion)
with increasing acid concentration
reaction with metal and acid produces
and kind of reactio
hydrogen + salt
redox reaction
a carbonate reacts with acid to produce
salt+ water+ carbon dioxide gas
