Chemistry - Reactivity Series and Redox

What can metals react with?

Water and acids

Examples of metals that all react strongly with water

Potassium, sodium, lithium, calcium

Metal + water →

Metal hydroxide + hydrogen

What do less reactive metals react with?

Steam but not water

Examples of metals that react with steam

Magnesium, zinc, iron

Magnesium + steam [Mg_(s) + H₂O_(g)] →

Magnesium oxide + hydrogen gas [MgO_(s) + H_2(g)]

What won’t react with water or steam?

Copper

Displacement

A more reactive metal displaces a less reactive metal during a chemical equation. often occurs with metal oxides

Zn + CuO →

ZnO + Cu

Many metal salts are ____ in water?

Soluble

What metal salts form aqueous solutions?

NaCl, ZnCl and CuSO₄

What happens when a more reactive metal is introduced to a solution of aqueous salt?

The more reactive metal will displace the less reactive metal in the salt

What is a displacement reaction often accompanied by?

A colour change in the solution

Colour change for Mg + CuSO₄ → Cu + MgSO₂ displacement reaction

Solution goes from blue to colourless

Solid goes from grey to red-brown

Reactivity series (metals) from most reactive to least reactive

Potassium, sodium, lithium, calcium, magnesium, aluminium, zinc, iron, copper, silver, gold

What does iron do?

Rust

What is rusting an example of?

Corrosion

What is corrosion?

The destruction of materials by chemical reactions within substances in the environment

When does iron rust?

When exposed to both oxygen and water

Rusting equation

Iron + water + oxygen → hydrated iron (III) oxide

4Fe + 2H₂O + 3O₂ → 2Fe₂O₃.H₂O

Why does the rust flaking off matter?

It exposes more iron which will then oxidise to form more rust

How can rusting be prevented without another metal?

Coating the oil with a barrier - paint it with plastic or coat it in oil and grease. This stops water and oxygen from reaching the iron

How can rusting be prevented with another metal?

Galvanisation

What is galvinisation?

When zinc is used to coat the iron. The zinc is more reactive than the iron so gets oxidised instead of the iron

What is galvanisation an example of?

Sacrificial protection, where one element is oxidised instead of the other

What does redox stand for?

Reduction and oxidation

What happens during redox reactions?

Something is reduced and something else is oxidised

What is reduction?

The gain of electrons and the loss of oxygen

What is oxidation?

The loss of electrons and the gain of oxygen

Redox pneumonic

Oxidation
Is

Loss
Reduction
Is

Gain

What is a reducing agent?

A substance that takes oxygen from other substances, or gives electrons to other substances

What are common reducing agents?

Metals

What is an oxidising agent?

A substance that takes electrons from other substances, or gives oxygen to other substances