Topic 4 Chemical Changes Flashcards
What happens when metals react with water or acid?
Lose electrons and form positive ions
Which 2 non-metals are included in the reactivity series?
Hydrogen and carbon
What is the order of metals in the reactivity series?
Potassium
Sodium
Lithium
Calcium
Magnesium
Carbon
Zinc
Iron
Hydrogen
Copper
What is the order of the top 5 metals in the reactivity series?
Potassium
Sodium
Lithium
Calcium
Magnesium
What is the order of the bottom 5 metals (and nonmetals) in the reactivity series?
Carbon
Zinc
Iron
Hydrogen
Copper
How else can the pH be measured other than using universal indicator?
pH probe
What do acids produce in aqueous solutions?
Hydrogen ions
What are bases?
insoluble metal hydroxides and metal oxides
What are alkalis?
Soluble metal hydroxides
What do aqueous solutions of alkalis contain?
Hydroxide ions
What is the difference between an alkali and a base?
Alkalis are bases that dissolve in water to form alkaline solutions
What is the word equation for a neutralisation reaction?
Acid + base > salt + water
In neutralisation reactions between an acid and alkali what do hydrogen ions and hydroxide ions react to form?
Water
What are titrations used for?
find reacting volumes of acid and alkali solutions
What is pH a measure of?
Concentration of hydrogen ions in a solution
What happens to a strong acid in aqueous solution?
Ionised completely (all acid particles dissociate to release H+ ions)
What are 3 examples of strong acids?
Sulfuric
Hydrochloric
Nitric
What are 3 examples of weak acids?
Ethanoic
Citric
Carbonic
What happens to a weak acid in aqueous solution?
Partially ionised (small proportion of acid particles dissociate to release H+ ions)
What is the concentration of an acid a measure of?
How much acid there is in a certain volume of water
What is an acids strength a measure of?
What proportion of acid molecules ionise in water
What type of reaction is a metal reacting with oxygen to produce metal oxides?
Oxidation
How are most metals in the earth found?
As compounds
How are unreactive metals such as gold found in the earth?
As the metal itself
What is an ore?
rock that contains enough of metal or metal compound to make extracting metal worthwhile
How can metals less reactive than carbon be extracted from their oxides?
By reduction with carbon
How can metals higher than carbon in the reactivity series be extracted?
Using electrolysis
In the reaction where a metal is extracted by reduction using carbon what is reduced?
ore as oxygen is removed
In the reaction where a metal is extracted by reduction with carbon what is oxidised?
Carbon as it gains oxygen
What type of reaction are displacement reactions?
REDOX
In displacement reactions what is always reduced?
Metal ion (gains electrons)
In displacement reactions what is always oxidised?
Metal atom (loses electrons)
What does an ionic equation only show?
Particles that react and products they form
What does an ionic equation for a displacement reaction only show?
Substances which are oxidised and reduced
What do some metals react with acid to produce?
salt and hydrogen
What is the word equation for a reaction between an acid and a metal?
Acid + metal > salt + hydrogen
What is the word equation for a reaction between a metal and water?
Metal + water > metal hydroxide + hydrogen
What is the word equation for a reaction between an acid and a metal carbonate?
Acid + metal carbonate > salt + water + carbon dioxide
How can soluble salts be made?
By reacting acid with insoluble base
What are the 3 steps to make soluble salts?
Add solid to acid until no more reacts
Filter out excess solid
Crystallise solution to produce solid salts
For every decrease of 1 on the pH scale, how does this affect the concentration of H+ ions?
Increases by factor of 10
What is the electrolyte?
Molten/dissolved ionic compound
What is the electrode?
Solid that conducts electricity and is submerged in electrolyte
What does passing an electric current through electrolytes cause?
Ions to move to electrodes
Which is the negative electrode?
Cathode
Where do the positive ions in the electrolyte move towards?
Cathode
What happens at the cathode?
Positive ions gain electrons- reduced
Which is the positive electrode?
Anode
Where do the negatively charged ions in the electrolyte move towards?
Anode
What happens at the anode?
Negative ions lose electrons- oxidised
What happens at the electrodes?
Ions are discharged producing elements
Why can molten ionic compounds be electrolysed?
Ions move freely and conduct electricity
Why is extracting metals via electrolysis very expensive?
Lots of energy to melt compounds and produce electrical current
Why does the anode need to be replaced regularly?
Made of carbon- reacts with oxygen to produce CO2
What molten mixture is aluminium extracted from via electrolysis?
Aluminium oxide and cryolite
Why is aluminium oxide mixed with cryolite (in the extraction of aluminium via electrolysis)?
Aluminium oxide has high melting point -to lower melting point
What is used as the anode in the extraction of aluminium via electrolysis?
Carbon
What is the chemical formula for aluminium oxide?
Al3O2
What happens to the aluminium ions in electrolysis (in the extraction of aluminium)?
Pick up 3 electrons at cathode
Turn into neutral aluminium atoms
Sink to bottom of electrolysis tank
What happens to the oxygen ions in electrolysis (in the extraction of aluminium)?
Lose 2 electrons at anode
Neutral oxygen atoms combine to form 02 molecules
What is also present in aqueous solutions as well as ions from the ionic compound?
Hydrogen ions and hydroxide ions from water
When will hydrogen gas be produced at the cathode?
Metal is more reactive than hydrogen
When will hydroxide ions be discharged and oxygen produced at the anode?
If no halide ions present
What are 3 halogens that could be produced at the anode?
Chlorine
Bromine
Iodine
What are inert electrodes?
Don’t react with electrolyte
What do half equations show?
Reactions at electrodes
