5.1.3 Single Displacement Reactions Explained

Key Concepts

1. Definition of Single Displacement Reactions

Single displacement reactions, also known as single replacement reactions, occur when an element in a compound is replaced by another element. This type of reaction involves the exchange of one element for another in a compound.

2. Reactivity Series

The reactivity series is a list of elements arranged in order of decreasing reactivity. Elements higher in the series can displace elements lower in the series from their compounds.

3. Types of Single Displacement Reactions

There are two main types of single displacement reactions: metal displacement and halogen displacement. Metal displacement involves a metal replacing another metal or hydrogen in a compound, while halogen displacement involves a halogen replacing another halogen in a compound.

4. Balancing Single Displacement Reactions

Balancing a single displacement reaction involves ensuring that the number of atoms of each element is the same on both sides of the reaction equation. This is done by adjusting the coefficients of the reactants and products.

Detailed Explanation

Definition of Single Displacement Reactions

In a single displacement reaction, an element from a compound is replaced by another element. This can be represented by the general equation:

A + BC → AC + B

where element A displaces element B from compound BC, forming new compounds AC and B.

Reactivity Series

The reactivity series helps predict whether a single displacement reaction will occur. For example, sodium (Na) is more reactive than hydrogen (H), so sodium can displace hydrogen from water:

2Na + 2H₂O → 2NaOH + H₂

In this reaction, sodium displaces hydrogen from water, forming sodium hydroxide and hydrogen gas.

Types of Single Displacement Reactions

Metal displacement reactions involve a metal replacing another metal or hydrogen in a compound. For example, zinc (Zn) can displace copper (Cu) from copper(II) sulfate (CuSO₄):

Zn + CuSO₄ → ZnSO₄ + Cu

Halogens can also undergo single displacement reactions. For example, chlorine (Cl₂) can displace bromine (Br₂) from potassium bromide (KBr):

Cl₂ + 2KBr → 2KCl + Br₂

Balancing Single Displacement Reactions

Balancing a single displacement reaction ensures that the law of conservation of mass is obeyed. For example, consider the reaction between magnesium (Mg) and hydrochloric acid (HCl):

Mg + 2HCl → MgCl₂ + H₂

Here, the coefficients are adjusted to ensure that there are equal numbers of magnesium, hydrogen, and chlorine atoms on both sides of the equation.

Examples and Analogies

Example: Metal Displacement

When iron (Fe) reacts with copper(II) sulfate (CuSO₄), iron displaces copper, forming iron(II) sulfate (FeSO₄) and copper (Cu):

Fe + CuSO₄ → FeSO₄ + Cu

This reaction occurs because iron is more reactive than copper.

Analogy: Single Displacement as a Relay Race

Think of single displacement reactions as a relay race. In a relay race, one runner (element) takes the baton (atom) from another runner (element) and continues the race (reaction). Similarly, in a single displacement reaction, one element takes the place of another in a compound.

Example: Halogen Displacement

When chlorine (Cl₂) reacts with sodium iodide (NaI), chlorine displaces iodine (I₂), forming sodium chloride (NaCl) and iodine (I₂):

Cl₂ + 2NaI → 2NaCl + I₂

This reaction occurs because chlorine is more reactive than iodine.