What is a Displacement Reaction? Definition, Equations & Examples
Displacement Reaction is essential in chemistry and helps students understand various practical and theoretical applications related to this topic.
What is Displacement Reaction in Chemistry?
A displacement reaction refers to a chemical reaction where a more reactive element replaces a less reactive element from its compound. This concept appears in chapters related to types of chemical reactions, reactivity series, and redox reactions, making it a foundational part of your chemistry syllabus.
Molecular Formula and Composition
Displacement reactions do not have a single molecular formula, as they are a category of chemical reactions. Instead, their general form is:
Single Displacement: A + BC → AC + B
Double Displacement: AB + CD → AD + CB
Elements and compounds involved depend on the specific reaction, often including metals, salts, acids, or bases.
Preparation and Synthesis Methods
Displacement reactions are commonly prepared by mixing a more reactive element with a compound containing a less reactive element. In labs, for example, placing an iron nail in copper sulfate solution triggers a displacement reaction. Industrially, they are used to extract metals from their oxides, as in the thermite process (Al + Fe2O3).
Physical Properties of Displacement Reaction
Physical properties relate to the reactants/products involved. What’s visually noticeable is generally a color change, gas evolution, or solid deposit. Temperature shifts may occur due to energy changes.
Chemical Properties and Reactions
Displacement reactions are mostly redox reactions, meaning electrons transfer from one substance to another. In single displacement, a free element replaces another in a compound (often seen in metal + salt solutions). In double displacement, ions in two compounds exchange partners, often forming a precipitate or gas. Typical reactions:
| Type | General Equation | Example |
|---|---|---|
| Single Displacement | A + BC → AC + B | Fe + CuSO4 → FeSO4 + Cu |
| Double Displacement | AB + CD → AD + CB | AgNO3 + NaCl → AgCl + NaNO3 |
Frequent Related Errors
- Confusing displacement reactions with neutralization or other reaction types.
- Wrongly identifying which reactant gets replaced/displaced.
- Mixing up single and double displacement reaction products.
- Ignoring the significance of metal reactivity series when predicting outcomes.
Uses of Displacement Reaction in Real Life
Displacement reactions are widely used in real life:
- Thermite welding to join railway tracks (Al + Fe2O3 → Al2O3 + Fe)
- Extraction of metals from ores (e.g., Fe from Fe2O3 using C)
- Antacid action in the stomach (Mg(OH)2 + 2HCl → MgCl2 + 2H2O)
- Electroplating to prevent corrosion (Zn displacing Fe on iron surfaces)
- Purification of water in precipitation reactions
Relevance in Competitive Exams
Students preparing for NEET, JEE, and Olympiads should be familiar with displacement reaction, as it often features in reaction-based and concept-testing questions. Knowing single vs double displacement and the reactivity series is critical for quick and correct answers.
Relation with Other Chemistry Concepts
Displacement reaction is closely related to topics such as chemical equations and double displacement reaction, helping students build a conceptual bridge between various chapters. It is also a type of redox reaction where electron transfer occurs.
Step-by-Step Reaction Example
1. Start with the reaction setup.Place a clean iron nail in a blue copper sulfate (CuSO4) solution.
2. Write the balanced equation.
Fe (s) + CuSO4 (aq) → FeSO4 (aq) + Cu (s)
3. Explain the intermediate or by-product.
The blue color fades (CuSO4 decreases), reddish copper deposit forms on the nail, and green FeSO4 is produced.
4. State reaction conditions.
Reaction occurs at room temperature in aqueous solution.
Final Answer: Iron displaces copper from copper sulfate, demonstrating the single displacement reaction.
Lab or Experimental Tips
Remember displacement reactions by the “metal higher in the reactivity series wins” rule. Vedantu educators often use the “iron nail in copper sulfate” tip in live sessions for quick demonstration and memory-building.
Try This Yourself
- Write the IUPAC name of FeSO4.
- Identify if copper can replace zinc in ZnSO4 solution.
- Give two real-life examples of displacement reaction applications.
Final Wrap-Up
We explored displacement reactions—examples, steps, and real-life uses. For more in-depth explanations and exam-prep tips, explore live classes and notes at Vedantu.
Types of Chemical Reactions
Reactivity Series
Chemical Reactions and Equations
Redox Reaction
FAQs on Displacement Reaction in Chemistry: Meaning, Types, and Examples
1. What is a displacement reaction in chemistry?
A displacement reaction, also known as a replacement reaction, is a chemical reaction where a more reactive element displaces a less reactive element from its compound. This happens because the more reactive element has a stronger tendency to lose electrons (for metals) or gain electrons (for non-metals). A classic example is the reaction between iron (Fe) and copper(II) sulfate (CuSO₄), where iron displaces copper to form iron(II) sulfate (FeSO₄) and copper metal.
2. What is the main difference between a single displacement and a double displacement reaction?
In a single displacement reaction, one element replaces another in a compound. A double displacement reaction, also called a metathesis reaction, involves an exchange of ions between two compounds. In essence, single displacement is a one-for-one swap, whereas double displacement is a partner swap.
3. How does the reactivity series help predict the outcome of a single displacement reaction?
The reactivity series (or activity series) orders elements according to their tendency to undergo reactions. In a single displacement reaction, a more reactive element (higher on the series) will displace a less reactive element (lower on the series) from its compound. For example, zinc (Zn) is more reactive than copper (Cu), so zinc will displace copper from copper(II) sulfate.
4. Can you provide some examples of a single displacement reaction?
Here are some examples:
- Zn + CuSO₄ → ZnSO₄ + Cu
- Fe + CuSO₄ → FeSO₄ + Cu
- Cl₂ + 2NaBr → 2NaCl + Br₂ (A more reactive non-metal displacing a less reactive one)
5. What are the different types of double displacement reactions, with examples?
Double displacement reactions are often categorized by their products. Common types include:
- Precipitation reactions: Two aqueous solutions react to form an insoluble solid (precipitate). Example: AgNO₃(aq) + NaCl(aq) → AgCl(s) + NaNO₃(aq)
- Neutralization reactions: An acid reacts with a base to form salt and water. Example: HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l)
6. Why is hydrogen, a non-metal, included in the metal reactivity series?
Hydrogen is included for comparative purposes. Its position helps predict whether a metal will displace hydrogen from acids or water. Metals above hydrogen in the series readily displace it; those below do not.
7. What are some real-world applications of displacement reactions?
Displacement reactions have many applications:
- Thermite welding: Joining railway tracks using aluminium displacing iron from iron(III) oxide.
- Extraction of metals: Obtaining less reactive metals from ores using more reactive metals.
- Antacids: Neutralizing excess stomach acid using bases (neutralization reaction).
- Electroplating: Coating a metal with another to improve appearance or prevent corrosion.
8. Can non-metals participate in displacement reactions?
Yes, non-metals can also participate in displacement reactions. A more reactive non-metal can displace a less reactive non-metal from its compound. The reactivity of non-metals is related to their tendency to gain electrons. For example, chlorine can displace bromine from sodium bromide.
9. How can displacement reactions be used to extract metals industrially?
Many metals are extracted from their ores using displacement reactions. A more reactive element (often carbon) is used to displace the metal from its compound, freeing the metal in its elemental form. This is a crucial process in metallurgy.
10. Are all displacement reactions also redox reactions?
Many, but not all, displacement reactions are also redox reactions (reduction-oxidation reactions). In redox reactions, electrons are transferred between the reactants. Many metal displacement reactions involve the transfer of electrons, but not all. For example, some double displacement reactions are not redox reactions.
11. What factors determine the spontaneity of a displacement reaction?
The spontaneity of a displacement reaction is determined by the relative reactivity of the elements involved and the change in Gibbs Free Energy (ΔG). A negative ΔG indicates a spontaneous reaction, meaning it will occur without external input. The reactivity series helps predict this, but a more precise prediction requires thermodynamic data.
