corrosion

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N3 -4
corrosion
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What is corrosion?
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A chemical reaction involving a metal changing
from an element to a compound
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Magnesium provides iron with sacrificial
protection. In which direction do electrons flow?
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From magnesium to iron
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Which metal is used to galvanise iron?
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zinc
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Which metal RUSTS?
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iron
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Give an example of how iron can be physically
protected.
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Paint, grease, tin-plate, electroplate,
galvanising, coat with plastic
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How does a physical barrier protect iron against
rusting?
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Barrier to water and air (oxygen)
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Which iron ion is formed when iron rusts?
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Fe2
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What name is given to the coating of iron with
zinc?
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galvanising
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Chromium plated steel rusts quickly when
scratched. Compared to iron is chromium more
reactive or less reactive.
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Less reactive
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Why does salt speed up corrosion?
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Salt is an electrolyte
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How does salt and acid rain affect corrosion?
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Speeds it up
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What is the test for Fe2 ions?
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Ferroxyl indicator turns blue
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What two conditions are required for rusting to
take place?
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Water and oxygen
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What type of reaction takes place when a metal
corrodes?
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oxidation