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
displacement reactions can be analysed in terms
redox reactions by studying the transfer of electrons
method to investigate metals reacting with acids
Wear some safety glasses before handling acids
Using a small measuring cylinder, add 5 cm3 of dilute hydrochloric acid to each of three test tubes
Add about 1 cm length of magnesium ribbon to the first tube, observe and note down what you see
Use a lighted splint to test for any gases given off
To the second test tube add a few pieces of iron filings and to the third some zinc turnings
Observe what happens, test for any gases and note down your observations
Repeat the experiment with dilute sulfuric acid
magnesium with dilute hydrochloric acid
Dissolves quickly, gets hot, gas given
off which goes pop with a lighted
splint, colourless solution left
magnesium with dilute sulfuric acid
rapid bubbling, splint goes pop, metal dissolves
iron with dilute hydrochloric acid
very slow bubbling
iron with dilute sulfuric acid
slow reaction, small bubbles seen
zinc with dilute hydrochloric acid
bubbles given off, metal slowly dissolving
zinc with dilute sulfuric acid
metal dissolves forming a colourless solution, gas given off slowly
magnesium with sulfuric acid equation
Mg + H2SO4 -> MgSO4 + H2
magnesium with hydrochloric acid equation
Mg + 2HCl -> MgCl2 + H2
zinc with sulfuric acid equation
Zn + H2SO4 -> ZnSO4 + H2
zinc with hydrochloric acid equation
Zn + 2HCl -> ZnCl2 + H2
iron with sulfuric acid equation
Fe + H2SO4 -> FeSO4 + H2
iron with hydrochloric acid equation
Fe + 2HCl -> FeCl2 + H2
conclusions of investigating metals reacting with acids
The metals can be ranked in reactivity order Mg > Zn > Fe
The three metals react in the same with both acids
Hydrogen and a metal salt solution is produced
