Double Displacement Reaction

 

Double Displacement Reaction:

A double displacement reaction (also called a double replacement or metathesis reaction) is a chemical reaction in which two compounds exchange their ions to form two new compounds. These usually occur in aqueous solutions and often result in the formation of a precipitate, gas, or neutral molecule like water.

General form:

AB + CD \rightarrow AD + CB

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Examples:

1. Reaction between Barium Chloride and Sodium Sulphate:

BaCl_2 + Na_2SO_4 \rightarrow BaSO_4 \downarrow + 2NaCl

(White precipitate of barium sulphate is formed.)

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2. Reaction between Sodium Hydroxide and Hydrochloric Acid (Neutralization):

NaOH + HCl \rightarrow NaCl + H_2O

(Water and salt are formed.)

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3. Reaction between Lead(II) Nitrate and Potassium Iodide:

Pb(NO_3)_2 + 2KI \rightarrow PbI_2 \downarrow + 2KNO_3

(Yellow precipitate of lead iodide is formed.)

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