What is Displacement Reaction?

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Grade Level:

Class 12

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Definition

What is it?

A displacement reaction is a chemical reaction where a more reactive element takes the place of a less reactive element in a compound. Think of it like a stronger player replacing a weaker player in a team.

Simple Example

Quick Example

Imagine you have a compound 'AB' and another element 'C'. If 'C' is more reactive than 'A', then 'C' will kick 'A' out and join with 'B' to form 'CB', leaving 'A' alone. It's like a new, faster auto-rickshaw driver (C) taking over a route from an older, slower driver (A), making the passengers (B) ride with the new driver.

Worked Example

Step-by-Step

Let's see how iron (Fe) reacts with copper sulphate (CuSO4) solution. Iron is more reactive than copper.

Step 1: Identify the reactants: Iron (Fe) and Copper Sulphate (CuSO4).
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Step 2: Identify the elements in the compound: Copper (Cu) and Sulphate (SO4).
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Step 3: Compare the reactivity: Iron (Fe) is more reactive than Copper (Cu).
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Step 4: The more reactive element (Fe) will displace the less reactive element (Cu) from its compound.
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Step 5: Iron will combine with sulphate to form Iron Sulphate (FeSO4), and Copper (Cu) will be left alone.
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Step 6: Write the balanced chemical equation: Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s).
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Answer: Iron displaces copper from copper sulphate, forming iron sulphate and copper metal.

Why It Matters

Understanding displacement reactions helps engineers design better materials and scientists develop new medicines. For instance, in biotechnology, these reactions are used to separate specific substances. They are also crucial in extracting metals from their ores, a key process in manufacturing for everything from mobile phones to electric vehicles.

Common Mistakes

MISTAKE: Assuming any element can displace another from a compound. | CORRECTION: Only a more reactive element can displace a less reactive element. Always check the reactivity series.

MISTAKE: Confusing displacement reactions with double displacement reactions. | CORRECTION: In a displacement reaction, one element replaces another. In double displacement, two compounds exchange ions.

MISTAKE: Not balancing the chemical equation after writing the products. | CORRECTION: Always ensure the number of atoms of each element is the same on both sides of the reaction arrow to follow the Law of Conservation of Mass.

Practice Questions

Try It Yourself

QUESTION: Which metal will displace hydrogen from dilute hydrochloric acid: Zinc (Zn) or Silver (Ag)? (Hint: Zinc is more reactive than hydrogen, silver is less reactive). | ANSWER: Zinc (Zn)

QUESTION: Write the balanced chemical equation for the reaction when magnesium metal is added to a solution of silver nitrate. (Hint: Magnesium is more reactive than silver). | ANSWER: Mg(s) + 2AgNO3(aq) → Mg(NO3)2(aq) + 2Ag(s)

QUESTION: A student puts an iron nail into a solution of copper chloride. Describe what happens and write the balanced chemical equation. Why does this happen? (Hint: Iron is more reactive than copper). | ANSWER: The iron nail will get coated with reddish-brown copper, and the blue copper chloride solution will become light green due to the formation of iron chloride. Equation: Fe(s) + CuCl2(aq) → FeCl2(aq) + Cu(s). This happens because iron is more reactive than copper and displaces copper from copper chloride.

MCQ

Quick Quiz

Which of the following reactions is a displacement reaction?

2H2 + O2 → 2H2O

AgNO3 + NaCl → AgCl + NaNO3

Zn + CuSO4 → ZnSO4 + Cu

CaCO3 → CaO + CO2

The Correct Answer Is:

Option C shows Zinc (an element) displacing Copper from Copper Sulphate (a compound), which is the definition of a displacement reaction. Options A, B, and D are combination, double displacement, and decomposition reactions respectively.

Real World Connection

In the Real World

Displacement reactions are essential in the purification of metals. For example, in India, during the extraction of metals like copper, a more reactive metal (like iron) is sometimes used to displace copper from its salt solutions, helping in the refining process to get pure copper for electrical wires and utensils.

Key Vocabulary

Key Terms

REACTIVE: How easily an element undergoes a chemical reaction | COMPOUND: A substance formed when two or more chemical elements are chemically bonded together | REACTIVITY SERIES: A list of metals in order of their reactivity from highest to lowest | DISPLACE: To take the place of something

What's Next

What to Learn Next

Next, you should learn about the 'Reactivity Series' to understand which elements are more reactive than others. This will help you predict the outcomes of displacement reactions much more accurately and apply this knowledge to more complex chemical processes.