🧪 Precipitation Reaction

 Certainly, Mayank! Here's a clear, CBSE-exam–oriented explanation of the Precipitation Reaction for Class 10 Science students, with definitions, examples, and concepts aligned with the NCERT syllabus.

🧪 Precipitation Reaction

(Class 10 Science – Chapter 1: Chemical Reactions and Equations)

📘 Definition:

A precipitation reaction is a type of chemical reaction in which two aqueous solutions react to form an insoluble solid called a precipitate.

✅ This precipitate appears as a solid that settles at the bottom of the reaction mixture.

🔬 General Form:

AB(aq)+CD(aq)→AD(s)↓+CB(aq)AB (aq) + CD (aq) \rightarrow AD (s) ↓ + CB (aq)

  • AB and CD are aqueous ionic compounds

  • AD is the precipitate (solid)

  • CB remains dissolved in water (aqueous)

🧪 Examples from NCERT / CBSE Class 10:

✅ 1. Barium Chloride + Sodium Sulphate

(Activity 1.10)

BaCl2(aq)+Na2SO4(aq)→BaSO4(s)↓+2NaCl(aq)\text{BaCl}_2 (aq) + \text{Na}_2\text{SO}_4 (aq) \rightarrow \text{BaSO}_4 (s) ↓ + 2\text{NaCl} (aq)

  • White precipitate of barium sulphate (BaSO₄) is formed

  • A classic double displacement + precipitation reaction

✅ 2. Lead(II) Nitrate + Potassium Iodide

(Activity 1.2 Recall)

Pb(NO3)2(aq)+2KI(aq)→PbI2(s)↓+2KNO3(aq)\text{Pb(NO}_3)_2 (aq) + 2\text{KI} (aq) \rightarrow \text{PbI}_2 (s) ↓ + 2\text{KNO}_3 (aq)

  • Forms bright yellow precipitate of lead(II) iodide (PbI₂)

📌 Characteristics of Precipitation Reactions:

Property Description
Type Double Displacement Reaction
Product One is an insoluble solid (precipitate)
Medium Occurs in aqueous (water) solutions
Detectable change Sudden appearance of a solid
Useful in Salt analysis, water purification, qualitative tests

🧠 CBSE Exam Tip:

Q: What is a precipitation reaction? Give one example with a balanced chemical equation.
✅ Answer:

A precipitation reaction is a chemical reaction in which two solutions react to form an insoluble solid, called a precipitate.

Example:

BaCl2(aq)+Na2SO4(aq)→BaSO4(s)↓+2NaCl(aq)\text{BaCl}_2 (aq) + \text{Na}_2\text{SO}_4 (aq) \rightarrow \text{BaSO}_4 (s) ↓ + 2\text{NaCl} (aq)

BaSO₄ is the white precipitate formed.

✅ Conclusion:

  • Precipitation reactions are evidence of chemical change.

  • They involve the formation of a solid from two liquid solutions.

  • Always write the state symbols in the equation for clarity in exams.

Would you like a visual concept map, MCQ quiz, or chalkboard diagram for class demonstration on this topic?

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