Reactivity series — KCSE Chemistry

Displacement reactions occur when a more reactive metal displaces a less reactive metal from its salt solution. The reactivity series ranks metals from most reactive to least reactive. For example, the series starts with potassium and sodium, followed by calcium, magnesium, aluminum, zinc, iron, lead, copper, silver, and gold.

In a displacement reaction, the general equation can be represented as:

Metal A + Salt Solution of Metal B → Salt Solution of Metal A + Metal B

To determine if a displacement reaction will occur, compare the reactivities of the metals involved. If Metal A is higher in the reactivity series than Metal B, a reaction will take place. If not, no reaction occurs.

Example: When zinc (Zn) is added to copper(II) sulfate (CuSO₄) solution:

• Zn + CuSO₄ → ZnSO₄ + Cu
• Zinc displaces copper because it is more reactive.

Conversely, if copper is placed in zinc sulfate (ZnSO₄):

• Cu + ZnSO₄ → No reaction
• Copper does not displace zinc as it is less reactive.

In a displacement reaction, a more reactive metal displaces a less reactive metal from its salt solution. To predict if a displacement reaction will occur, refer to the reactivity series of metals. The reactivity series ranks metals from most reactive to least reactive.

Key points to remember:

• A metal can displace another metal from its salt if it is higher in the reactivity series.
• If the metal is lower, no reaction occurs.
• Common metals in the series include potassium, sodium, calcium, magnesium, aluminum, zinc, iron, lead, copper, silver, and gold.

Example: If you have zinc (Zn) and copper(II) sulfate (CuSO₄), you can predict the reaction:

• Zinc is above copper in the reactivity series.

• Therefore, zinc will displace copper from copper(II) sulfate, resulting in the reaction:

  Zn + CuSO₄ → ZnSO₄ + Cu

In contrast, if you have copper (Cu) and zinc sulfate (ZnSO₄):

• Copper is below zinc in the reactivity series.
• No reaction will occur as copper cannot displace zinc.

The reactivity series is a list of metals arranged in order of their reactivity from highest to lowest. It helps predict how metals will react in different situations, particularly with water, acids, and other metals. Key points to remember:

• Potassium and sodium are highly reactive and can react vigorously with water.
• Calcium, magnesium, and aluminum react with acids and water but less violently than potassium and sodium.
• Zinc, iron, and lead are moderate in reactivity, reacting with acids but not with water.
• Copper, silver, and gold are low in reactivity and do not react with water or dilute acids.

Understanding the reactivity series is crucial for predicting displacement reactions. For example, a more reactive metal can displace a less reactive metal from its compound.

When considering reactions, remember:

• Reactivity decreases down the group.
• The series is essential in metallurgy and electrochemistry.