1reactivity series Flashcards
the chemistry of metals is studied
by analysing their reactions with water and acids
reaction for calcium and water is
Ca (s) + 2H2O (l) ⟶ Ca(OH)2 (aq) + H2(g)
calcium + water ⟶ calcium hydroxide + hydrogen
what metals on the reactivity series will react with dilute acids
above hydrogen
the more reactive a metal is
the more vigorous the reaction will be
metals such as potassium and sodium are
very dangerous and react explosively with acids
when acids react with metals they form
a salt and hydrogen gas
acid-metal reaction equation
metal + acid -> salt + hydrogen
a more reactive metal will
displace a less reactive metal
the reactivity of two metals can be compared using
the displacement reactions in salt solutions of one of the metals - this is easily seen as the more reactive metal slowly disappears from the solution, displacing the less reactive metal
reactivity series
Potassium Sodium Lithium Calcium Magnesium Aluminium Carbon Zinc Iron Hydrogen Copper Silver Gold
rusting is
the chemical reaction between iron, water and oxygen to form hydrated iron(III) oxide
what must be present for rust to occur
oxygen and water
rusting is a
redox process and it occurs faster in salty water since the presence of sodium chloride speeds up the reaction
rust equations
Iron + Water + Oxygen → Hydrated Iron(III) Oxide
4Fe (s) + 3O2 (g) + xH2O (l) → 2Fe2O3.xH2O (s)
method to investigate rusting
Set up the apparatus as shown in the diagram
The water in the second test tube is boiled to remove any dissolved oxygen
The oil provides a barrier to prevent oxygen diffusing into the boiled water
Calcium chloride is a drying agent in the third test tube
Leave the apparatus for a few days to give it time to react
results of investigating rusting
The nail on the left rusts as it is in contact with both air (which contains oxygen) and water
The nail in the middle does not rust as it is not in contact with air
The nail on the right does not rust as it is not in contact with water (calcium chloride absorbs any water molecules present due to moisture)
The results show that both air and water must be present for rusting to occur
damage to iron structures
Rust is a soft solid substance that flakes off the surface of iron easily, exposing fresh iron below which then undergoes rusting
This means that over time all of the iron rusts and its structure becomes weakened
barrier methods to prevent rusting
Rust can be prevented by coating iron with barriers that prevent the iron from coming into contact with water and oxygen- example is paint or grease
However, if the coatings are washed away or scratched, the iron is once again exposed to water and oxygen and will rust
galvanising
the process where the iron to be protected is coated with a layer of zinc
sacrificial corrosion
Sacrificial corrosion occurs when a more reactive metal is intentionally allowed to corrode
An example of this occurs with ships’ hulls which sometimes have large blocks of magnesium or magnesium alloys attached
The blocks slowly corrode and provide protection to the hull in the same way the zinc does by pushing electrons onto the iron which prevents it from being reduced to iron(III) ions
oxidation
any reaction where the substance gains oxygen
reduction
when a substance loses oxygen
reducing agent
when something removes oxygen
oxidising agent
when something supplies oxygen
