#ReactivitySeries

#Chemistry

#ExplainingReactivity

What is the reactivity series of metals?

• The chemistry of the metals is studied by analysing their reactions with water and acids

• Based on these reactions a reactivity series of metals can be produced

• The series can be used to place a group of metals in order of reactivity based on the observations of their reactions with water and acids

• The non-metals hydrogen and carbon are also included in the reactivity series as they are used to extract metals from their oxides

  
  

Reaction of metals with cold water

• The more reactive metals will react with cold water to form a metal hydroxide and hydrogen gas

• Potassium, sodium and calcium all undergo reactions with cold water as they are the most reactive metals:

metal + water →  metal hydroxide + hydrogen

•  For example, calcium and potassium:

Ca (s) + 2H2O (l) → Ca(OH)2 (aq) + H2 (g)

2K (s) + 2H2O (l) → 2KOH (aq) + H2 (g)

Reactions of metals with steam

• Metals just below calcium in the reactivity series do not react with cold water but will react with steam to form a metal oxide and hydrogen gas, for example, magnesium:

Mg (s) + H2O (g)  →  MgO (s) + H2 (g)

Reaction with dilute acids

• Only metals above hydrogen in the reactivity series will react with dilute acids

• Unreactive metals below hydrogen, such as gold, silver and copper, do not react with acids

• The more reactive the metal then the more vigorous the reaction will be

• Metals that are placed high on the reactivity series 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:

• The general equation is:

metal + acid ⟶ salt + hydrogen

Reaction with oxygen

• Some reactive metals, such as the alkali metals, react easily with oxygen

• Silver, copper and iron can also react with oxygen although much more slowly

• When metals react with oxygen a metal oxide is formed, for example, copper:

metal + oxygen → metal oxide 

2Cu (s) + O2 (g) → 2CuO (s)

• Gold does not react with oxygen

Deducing the order of reactivity

• The order of reactivity of metals can be deduced by making experimental observations of reactions between metals and water, acids and oxygen

• The more vigorous the reaction of the metal, the higher up the reactivity series the metal is

• A combination of reactions may be needed, for example, the order of reactivity of the more reactive metals can be determined by their reactions with water

• The less reactive metals react slowly or not at all with water, so the order of reactivity would need to be determined by observing their reactions with dilute acid

• Temperature change in a reaction can also be used to determine the order of reactivity

• The greater the temperature change in a reaction involving a metal, the more reactive the metal is