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Chemistry Precipitation


What is a precipitate?

An insoluble solid formed by the reaction between two soluble substances is called a precipitate

The process is called precipitation.

The reactions in which precipitate formed is called precipitation reactions.

Experiment to show the precipitation reactions

Take a test tube and mix 1 ml. of aqueous solution of silver nitrate and 1 ml. of aqueous solution of sodium chloride .A milky white precipitate is formed.

How can we prove that it is a precipitate:

  • Look at the product and see if it is opaque or not clear
  • Try another reaction

                Mix 1 ml. of lead nitrate and 1 ml. of potassium iodide, a    yellow precipitate is formed.

  • Look in the Data Book

                 Look colour of lead iodide and silver chloride. Then look for their solubility

Ionic equation

Na Cl + AgNO3         NaNO3+Ag Cl

Ag + + Cl       AgCl    these are the reacting ions

Na+ + and NO3–   ions do not react so they are spectator ions

This equation is called the ionic equation for the reaction.