Chemistry: Activity Series Introduction

Study Notes

The Activity Series: An Introduction

The activity series is a tool used to predict the outcome of reactions involving metals and their compounds.
Metals are ordered from most to least reactive based on their ability to displace (replace) other metals in single displacement reactions.
In single displacement reactions, a more reactive metal will displace (replace) a less reactive metal in a compound.

Constructing the Activity Series

The activity series is determined experimentally by observing reactions between metals and various substances such as acids, water, and metal salts.
The general pattern observed:
- Highly reactive metals are at the top of the list and react readily with water and acids (e.g., alkali metals like lithium, sodium, potassium).
- Moderately reactive metals are in the middle of the list and react with acids but not with water (e.g., zinc, iron, nickel).
- Less reactive metals are at the bottom of the list and do not react with water or acids under normal conditions (e.g., silver, gold, platinum).

Understanding the Activity Series

The activity series reflects the tendency of metals to lose electrons and form positive ions (cations).
Highly reactive metals readily lose electrons, forming cations.
Less reactive metals do not easily lose electrons.

Single Displacement Reactions

A general equation for single displacement reactions is: A + BC → AC + B.
In this equation, A is a metal more reactive than B in the compound BC.
If A is higher in the activity series than B, the reaction will proceed. Otherwise, no reaction occurs.

Examples of Single Displacement Reactions

Zinc (Zn) is higher in the activity series than copper (Cu), so zinc displaces copper from copper sulfate (CuSO₄), resulting in the formation of zinc sulfate (ZnSO₄) and elemental copper (Cu): Zn + CuSO₄ → ZnSO₄ + Cu.
Copper (Cu) is lower in the activity series than zinc (Zn) so copper cannot displace zinc from zinc sulfate (ZnSO₄), resulting in no reaction: Cu + ZnSO₄ → No Reaction.

The Activity Series and Hydrogen

Hydrogen appears in the activity series as a reference point.
Metals above hydrogen are more reactive and can displace hydrogen from acids.
Metals below hydrogen are less reactive and cannot displace hydrogen from acids.

Examples of Reactions with Hydrogen

Zinc (Zn) is above hydrogen in the activity series, so zinc can displace hydrogen from hydrochloric acid (HCl), resulting in the formation of zinc chloride (ZnCl₂) and hydrogen gas (H₂): Zn + 2HCl → ZnCl₂ + H₂.
Copper (Cu) is below hydrogen in the activity series, so copper cannot displace hydrogen from hydrochloric acid, resulting in no reaction: Cu + 2HCl → No Reaction.

Reactivity of Metals with Water

Highly reactive metals react vigorously with cold water, producing hydroxides and hydrogen gas (e.g., 2Na + 2H₂O → 2NaOH + H₂).
Less reactive metals will react with hot water or steam (e.g., Mg + H₂O (steam) → MgO + H₂).
Metals below hydrogen in the activity series do not react with water under normal conditions.

Applications of the Activity Series

Metal extraction: The activity series helps determine extraction methods for metals from their ores.
Corrosion prevention: The activity series plays a role in methods used to prevent corrosion.
Electrochemistry: The activity series relates to electrode potentials in electrochemistry, helping understand electron flow in electrochemical cells.
Displacement Reactions in Industry: The activity series is used in industrial processes involving displacement reactions.

Limitations of the Activity Series

The reactivity of metals can vary with temperature and concentration, which may affect predictions made using the activity series.
The activity series is primarily for simple single displacement reactions, and may not be applicable to more complex reactions.
The activity series does not account for the reactivity of non-metals.

Conclusion

The activity series is a fundamental concept in chemistry, providing valuable insights into the reactivity of metals and helping to predict the outcomes of chemical reactions.

Description

Explore the activity series, a crucial concept in chemistry that helps predict metal reactivity in single displacement reactions. This quiz covers the ranking of metals from most to least reactive and how these observations are experimentally determined. Test your understanding of highly reactive, moderately reactive, and less reactive metals.