Question

Which one of the following reactions is different from the remaining three?

• A. NaCl + AgNO₃ → AgCl + NaNO₃
• B. CaO + H₂O → Ca(OH)₂
• C. KNO₃ + H₂SO₄ → KHSO₄ + HNO₃
• D. ZnCl₂ + H₂S → ZnS + 2HCl

Answer 1

The Correct Option is B

Step 1: Understanding the types of reactions:
We need to identify the type of each reaction to determine which one is different from the remaining three. Let's break down each reaction.

Step 2: Analyzing each reaction:

1. NaCl + AgNO₃ → AgCl + NaNO₃
   This is a double displacement reaction (also called a precipitation reaction) where the ions of two compounds are exchanged to form two new compounds.
   
   
2. CaO + H₂O → Ca(OH)₂
   This is a combination reaction (also called a synthesis reaction), where two reactants, calcium oxide (CaO) and water (H₂O), combine to form a single product, calcium hydroxide (Ca(OH)₂).
   
   
3. KNO₃ + H₂SO₄ → KHSO₄ + HNO₃
   This is another double displacement reaction, where the ions of two compounds, potassium nitrate (KNO₃) and sulfuric acid (H₂SO₄), are exchanged to form two new compounds.
   
   
4. ZnCl₂ + H₂S → ZnS + 2HCl
   This is also a double displacement reaction, where zinc chloride (ZnCl₂) and hydrogen sulfide (H₂S) exchange ions to form zinc sulfide (ZnS) and hydrochloric acid (HCl).
   
   

Step 3: Identifying the different reaction:
- Reactions 1, 3, and 4 are all double displacement reactions because they involve the exchange of ions between two reactants to form new compounds.
- Reaction 2 is a combination reaction, where two reactants combine to form a single product.

Step 4: Conclusion:
The reaction that is different from the others is:

CaO + H₂O → Ca(OH)₂

because it is a combination reaction, while the others are double displacement reactions.