Test: Types Of Displacement Reactions - UPSC MCQ

In the given reaction, barium hydroxide reacts with ammonium chloride. The products X and Y are identified through the balanced chemical equation.

The balanced reaction is:
Ba(OH)₂+2NH₄Cl→BaCl₂+2NH₄OH 
The correct option is therefore A.

To determine which of the given reactions is an example of a displacement reaction, we need to understand that in a displacement reaction, a more reactive element displaces a less reactive element in a compound.

The correct answer is C:
- Magnesium (Mg) displaces hydrogen (H) in hydrochloric acid (HCl) to form magnesium chloride (MgCl₂) and hydrogen gas (H₂).
- This reaction fits the criteria of a displacement reaction where a more reactive metal displaces a less reactive metal in a compound.

To identify the reaction between AgNO3(aq) and KCl(aq) as a precipitation reaction:

- Explanation:
- The reaction forms a solid precipitate, AgCl, which is insoluble.
- This type of reaction involves the exchange of ions to form an insoluble product.
- This is a classic example of a precipitation reaction.

Therefore, the correct answer is:
- C: Precipitation reaction
Precipitation is the creation of a solid from a solution. When the reaction occurs in a liquid solution, the solid formed is called the 'precipitate'. The chemical that causes the solid to form is called the 'precipitant'.

The above reaction is an example of displacement reaction as in the above reaction the elemental Zinc is displacing hydrogen from the compound of hydrochloric acid which is released in the form of hydrogen gas. The Zinc then combines with Chlorine to form Zinc Chloride.

A silver spoon should be used to stir lead nitrate solution because silver is less reactive than lead. In a displacement reaction, a more reactive metal can displace a less reactive metal from its compound. Since silver is less reactive than lead, it will not react with lead nitrate, preventing any displacement reaction. Thus, using silver is safe and appropriate in this case.

The metal that comes below copper in the reactivity series is Silver (C)
Explanation:
The reactivity series ranks metals based on their reactivity from highest to lowest.

• Copper is less reactive than Aluminium, Iron, and Zinc.
• Silver is less reactive than Copper, placing it below Copper in the series.
• Therefore, the correct answer is Silver (C).

In the reactivity series of metals, the order from most reactive to least reactive is typically:

1. Potassium
2. Sodium
3. Calcium
4. Magnesium
5. Aluminium
6. Zinc
7. Iron
8. Tin
9. Lead
10. Copper
11. Silver
12. Gold

Based on this series, silver comes below copper in the reactivity series.

The reaction between lead nitrate and potassium iodide is an example of a double displacement reaction.
Explanation

• Reaction Overview: When lead nitrate (Pb(NO₃)₂) reacts with potassium iodide (KI), they exchange ions.
• Products Formed: This reaction results in the formation of lead iodide (PbI₂) and potassium nitrate (KNO₃).
• Balanced Chemical Equation:
  Pb(NO₃)₂ + 2KI → PbI₂ + 2KNO₃

Concept Behind the Reaction

• Double Displacement Reaction: In this type of reaction, the cations and anions of two different compounds switch places, forming two new compounds. Here, the Pb²⁺ from Pb(NO₃)₂ swaps places with the K⁺ from KI.
• Visual Indication: A characteristic yellow precipitate of PbI₂ forms, indicating the occurrence of the reaction.
• Real-World Example: Such reactions are common in various chemical processes, including those in educational laboratory experiments.

The correct answer is option B.

The given equation is a displacement reaction in which Fe of Fe₂O₃ has been displaced by Al. Hence, (c) is the correct option.

The other metals are less reactive than zinc.

Inactivity series silver is placed below the copper. hence copper is more reactive than silver. The more reactive element can displace the less reactive element from its solution.

The colours of aqueous solutions of CuSO₄ and FeSO₄ as observed in the laboratory are dark blue and pale green respectively.

A displacement reaction is one in which a more reactive element displaces a less reactive element from its salt solution.

But copper can not lose electrons easily as compared to zinc and do not result in any reaction.

Thus there will no color change as no chemical reaction take place between the two.

Decomposition reactions require energy either in the form of heat or light or electricity for breaking down the reactants.

• When an iron nail is immersed in a copper sulfate solution, a displacement reaction occurs.
• In this reaction, iron displaces copper from copper sulfate solution, leading to the formation of iron sulfate and metallic copper.
• This explains why the iron nail turns brownish and the blue color of the copper sulfate solution fades, showcasing a classic example of a displacement reaction.

• The Assertion is true as the iron nail indeed becomes brownish and the blue color of the copper sulfate solution fades due to the displacement reaction described.
• The Reason is also true as iron displaces copper from the copper sulfate solution.
• The Reason is the correct explanation of the Assertion because the observed color changes are a direct result of the displacement reaction where iron replaces copper in the solution.