C4 Chemical Change Flashcards
What is the definition of oxidation?
Oxidation of a metal is the reaction where oxygen is added to form an oxide
What is the definition of reduction of a metal oxide?
where oxygen is removed from a metal
Why do most metals form oxides?
Most metals react with oxygen present in the atmosphere
Why doesn’t gold oxidise?
Gold is unreactive, so does not form an oxide
Each metal’s tendency to react is different. What does this relate to?
it is related directly to their electron structures.
how does calcium react with cold water?
Fizzes, vigorous, produces heat, colourless solution forms
how does calcium react with acid?
Fizzes, dissolves, colourless solution forms
how does copper react with cold water?
no reaction
how does copper react with acid?
no reaction
how does magnesuim react with cold water?
Appears to be no reaction (very slow)
how does madnesium react with acid?
Fizzes, dissolves, colourless solution forms
how does iron react with cold water?
Appears to be no reaction (very slow)
how does iron react with acid?
Fizzes, dissolves, colourless solution forms
(not as vigorous as Mg)
how does zinc react with cold water?
Virtually no reaction with cold water
how does zinc react with acid?
Reacts quickly, fizzes, dissolves, colourless solution forms
what is the reactivity series from most to least
Potassium
Sodium
Lithium
Calcium
Magnesium
Zinc
Iron
Copper
As we go down group I, reactivity increases. why?
As we go down the group, we increase the amount of shielding between the nucleus and outer shell electron (number of shells between them).
This makes it easier to remove the electron as we move down the group because the electron is not held as tightly.
Explain why calcium is more reactive than Magnesium.
Calcium is more reactive than magnesium because the outer electron is further from the nucleus and there is greater electron shielding, all of which reduce the attraction between electron and nucleus, making it easier for the electron to be lost.
what happens in a dispacment reaction?
A more reactive metal will displace a less reactive metal.
how does lithium react with oxygen in the air?
Shiny surface slowly goes dull (tarnishes).
how does lithium react with water?
Floats, fizzes, moves around slowly.
how does sodium react with oxygen in the air?
Shiny surface quickly goes dull (tarnishes).
how does sodium react with water?
Floats, fizzes,
moves rapidly,
Melts. May be orange flame.
how does potassium react with oxygen in the air?
Shiny surface very quickly goes dull (tarnishes).
how does potassium react with water?
Floats, fizzes,
moves very rapidly,
melts. Lilac flame as hydrogen gas catches fire.
what is an ore?
An Ore is a rock containing enough metal to make it economically viable to extract it
metals found in ores are found where?
the earths crust
metals found in ores in the earths crust are unreactive or reactive?
NATIVE METALS
Unreactive
metals found in ores are usually combined with …………… or ……….
sulfur or oxygen
metals found in ores Other elements ……….. to make metal ……….
Other elements removed to make metal useful
in the bisness of metal extraction what do you have to take into account with the product?
How easy is the ore to find
How easy is the ore to mine?
What method of extraction do I use?
in the bisness of metal extraction what do you have to take into account with the price?
How much to mine?
How much to extract the metal (energy costs)
Market value?
in the bisness of metal extraction what do you have to take into account with the place?
Where do I mine?
Is there a local workforce?
Impact on the environment
in the bisness of metal extraction what do you have to take into account with the promotion?
Who will buy it?
Where can I sell it?
Is there demand for my product?
Metals more rective than carbon in the reactivity series are removed from ore by ………?
Metals more reactive than carbon in the reactivity series are removed from ore by ELECTROLYSIS
If carbon is more reactive than a metal, it will react with a metal oxide to leave behind a …….. ………….and ………… ………..
If carbon is more reactive than a metal, it will react with a metal oxide to leave behind a pure metal and carbon dioxide.
METAL OXIDE + CARBON =
= METAL + CARBON DIOXIDE
what happens in a reduction with carbon?
The metal is reduced by carbon because it has the oxygen removed
Aluminium chloride + Magnesium →
Magnesium chloride + aluminium
Lithium bromide + Zinc (II) →
NO REACTION
Lead (II) sulfate + Calcium →
Calcium sulfate + Lead (II)
Potassium iodide + tin (IV) →
NO REACTION
Silver (I) nitrate + copper (II) →
Copper (II) nitrate + Silver (I)
Gold (II) oxide + hydrogen →
Gold (I) + water
how can you measure the pH of a solution?
by using an indicator, its a dye that changes colour depending on whether its above or below a certain pH or by using a pH probe, this is more accurate as the machine gives you a number.
what is an acid?
a substance that forms an aqueous solution with a pH of less than 7. acids form H+ ions in water.
what is a base?
a substance that will react with an acid to form a salt
what is an alkali?
a base that dissolves in water to form a solution with a pH greater than 7. alkalis form OH- ions in water
what is the reaction between acids and bases called?
neutalisation
what is the equation reaction between acids and bases?
acid + base -> salt + water
what does the neutralisation between acids and alkalis look like in terms of H+ and OH- ions?
H+ + OH- -> H2O
what do acids produce in water?
protons
what do strong acids do in water
strong acids ionise completely in water, all the acid particles dissociate to releases H+ IONS.
what do weak acids do in a soloution?
they do not fully ionise, only a small proportion of acid particles dissociate to relaese H+ ions
the ionisation of a weak acid is a reversible reaction which ……………..
sets up an equilibrium between the undissociated and dissociated acid
how do you work out the factor the hydrogen ion concentration?
final pH - starting pH = x
10 ^-(-x) = answer
what does the concentration measure?
how much acid there is in a certain volume of water
pH will ………. with increasing acid concentration
decreases
what metal oxides and metal hydroxides dissolve in water
alkalis
all metal oxides and metal hydroxides react with acids to form
a salt and a water
how do you make soluble salts using an insoluble base
1) pick an acid and insoluble base such as insoluble hydroxide, metal oxide or carbonate
2) gently warm the dilute acid using a Bunsen burner, then turn off the Bunsen burner
3) add the insoluble base to the acid a bit at a time until no more reacts.
4) then filter out the excess solid to get the salt solution
5) to get pure solid salt crystals , gently heat the solution using a water bath or an electric heater to evaporate some of the water ( to make it more concentrated) and then stop heating it and leave the solution to cool. crystals of the salt should form, which can be filtered out of the solution and then dreid.
what is a loss of electrons called
oxidation
what is a gain of electrons called
reduction
OIL RIG
OXIDATION IS LOSS
REDUCTION IS GAIN
examples of redox reactions
metals reacting with acids
halogen displacement reactions
how does electrolysis work?
a current is passed though an electrode. the electrode is a molten or dissolved ionic compound (so that the ions are free to move)
ions move towards electrodes where they react and the compound decomposes
the positive ions in the electrode will move towards the cathode (-) and gain electrons
the negative ions in the electrode will move towards the anode (+) and lose electrons
this creates a flow of change through the electrode as ions travel to the electrodes
as ions gain or lose electrons they form the uncharged element and are discharged from the electrode
why cant an ionic solid not be electrolysed?
because the ions are in fixed positions and cant move
why can molten ionic compounds be electrolysed?
because the ions can move freely and conduct electricity
molten ionic compounds are always……….
broken up into their elements
how can metals be extracted from their ores using electrolysis? example
aluminium is extracted from the ore bauxite by electrolysis. bauxite contains aluminium oxide
alimimnoum oxide has a very high melting temperature so its mixed with cryolite to lower the melting point
the molten mixture contains free ions so it’ll conduct electricity
the positive aluminium ions (Al^3+) are attracted to the negative electrode where they each pick up 3 electrons and turn into neutral aluminium ions. these sink to the bottom of the tank
the negative oxygen ions (o^2-) are attracted to the positive electrode where they each loose two electrons the neutral oxygen atoms will then combine to form o2 molecules
what are metals attracted to in electrolysis?
the negative electrode
what are non metals attracted to in electrolysis?
the positive electrode
why is cryolite used in electrolysis
to lower the melting point, which reduces the amount of energy needed ans saves money
why is electrolysis expensive?
melting the compound requires a lot of energy
a lot of energy is required to produce the electrical current
using energy is expensive
