4: Chemical Changes Flashcards
what is a redox reaction?
reactions that involve the addition or removal of oxygen from a substance
what happens in an oxidation reaction?
oxygen is added to an element or a compound; electrons are lost
what happens in an reduction reaction?
oxygen is removed from an element or a compound; electrons are gained
give the reactivity series (from most reactive to least).
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potassium, sodium, lithium, calcium, magnesium, aluminium, zinc, iron, copper, silver, gold
what is a displacement reaction?
when a more reactive metal will displace a less reactive metal from its oxide by heating
how can we compare the reactivity between two metals using displacement reactions in salt solutions of one of the metals?
the more reactive metal slowly disappears from the solution, displacing the less reactive metal, the less reactive metal will form a solid; when a less reactive metal is placed in the solution, it will not disappear; observe effervescence, precipitates and colour change
what are metal ores?
when metals in the earth’s crust are (naturally) chemically combines w other substances e.g. oxygen
how can metals be extracted from metal ores?
electrolysis, using a blast furnace or by reacting with more reactive material
what kind of reaction is it if the ore is an oxide of the metal?
reduction
why do unreactive metals do not have to be extracted chemically?
they are often found as the element alone; do not tend to react w other substances - have chemical stability
which metals are more resistant to being oxidised?
metals lower on the reactivity series - the higher it is, the more easily is can be oxidised
how can potassium, sodium, lithium, calcium, magnesium and aluminium be extracted from their metal ores?
they cannot be reduced by carbon or other reducing agents; they have to be extracted by electrolysis of the molten ore - this is expensive as it requires huge amount of energy/electricity to do
how can zinc, iron and copper be extracted from their metal ores?
can be reduced by heating w reducing agents e.g. C, CO, in a blast furnace; more economical - carbon is cheap and can be a source of heat as well so less energy/electricity needed
why is iron important?
large scale use of iron in industry and society
what is the symbol for electrons in ionic equations?
e^-
