Reactivity Series and Displacement Reactions - SS2 Chemistry Lesson Note
The reactivity series and displacement reactions are concepts used to understand and predict the behaviour of metals in chemical reactions. The reactivity series arranges metals in order of their reactivity, while displacement reactions involve the transfer of ions between metals based on their relative reactivity.
Reactivity Series:
The reactivity series is a list of metals arranged in order of their reactivity towards chemical reactions. It allows us to compare and predict the behaviour of different metals in various reactions. The most reactive metals are at the top of the series, while the least reactive metals are at the bottom.
Common Reactivity Series:
The common reactivity series, from most reactive to least reactive, includes:
1. Potassium (K)
2. Sodium (Na)
3. Calcium (Ca)
4. Magnesium (Mg)
5. Aluminium (Al)
6. Zinc (Zn)
7. Iron (Fe)
8. Lead (Pb)
9. Hydrogen (H)
10. Copper (Cu)
11. Silver (Ag)
12. Gold (Au)
Key Points about the Reactivity Series:
● Reactivity Trends: The reactivity of metals tends to increase as we move down the series. The higher a metal is in the series, the more reactive it is.
● Displacement Reactions: The reactivity series allows us to predict the outcome of displacement reactions, where a more reactive metal displaces a less reactive metal from its compound.
● Extraction of Metals: The reactivity series also helps in understanding the extraction of metals. Highly reactive metals, such as potassium and sodium, are extracted by electrolysis, while less reactive metals, like copper and silver, can be obtained by other methods.
Displacement Reactions:
Displacement reactions involve the transfer of ions between metals based on their relative reactivity. In a displacement reaction, a more reactive metal displaces a less reactive metal from its compound.
General Form of a Displacement Reaction:
Metal A + Metal B's compound → Metal B + Metal A's compound
Example:
Zinc (Zn) + Copper sulphate (CuSO4) → Copper (Cu) + Zinc sulphate (ZnSO4)
Key Points about Displacement Reactions:
● Reactivity Determines Displacement: In a displacement reaction, a metal higher in the reactivity series displaces a metal lower in the series from its compound.
● Ionic Equations: Displacement reactions can be represented by balanced ionic equations, showing the transfer of ions between the metals.
● Precipitation Reactions: Displacement reactions can also occur in solutions, leading to the formation of precipitates when an insoluble compound is formed.
Significance of Reactivity Series and Displacement Reactions:
● Predicting Reactivity: The reactivity series helps predict the behaviour of metals in reactions. More reactive metals readily lose electrons and are more likely to form positive ions.
● Extraction and Purification of Metals: The reactivity series guides the selection of suitable methods for the extraction and purification of metals. Highly reactive metals require more energy-intensive processes, while less reactive metals can be obtained by simpler methods.
● Corrosion and Rusting: Understanding the reactivity series helps explain phenomena such as corrosion and rusting. Metals higher in the series, like iron, readily react with oxygen and moisture, leading to the formation of oxides and corrosion.
● Industrial Applications: Knowledge of displacement reactions is essential in various industrial processes, including metal refining, electroplating, and the production of alloys.
● Redox Reactions: Displacement reactions are examples of redox (reduction-oxidation) reactions, where there is a transfer of electrons between species.
The reactivity series and displacement reactions are important concepts in understanding the behaviour of metals in chemical reactions. The reactivity series provides a hierarchical arrangement of metals based on their reactivity, allowing predictions of displacement reactions and insights into extraction processes. Displacement reactions demonstrate how a more reactive metal can displace a less reactive metal from its compound. Understanding the reactivity series and displacement reactions has significant implications in various fields, including metal extraction, corrosion prevention, and the production of alloys and other metal-based materials.