How to Distinguish Between HCL and HF

HCl and HF are chemical formula for hydrochloric and hydrofluoric acids. These two structurally similar inorganic acids have different properties. Hydrochloric acid completely dissociates in water, forming chloride and hydrogen ions, but HF is a weak acid that insignificantly dissociates in water. Distinguishing between these two compounds is a frequent laboratory assignment in chemistry. Silver nitrate (AgNO3) is a distinctive reagent for chloride ions that allows you to accomplish this task.

Things You'll Need

• Silver nitrate -- 5 percent solution
• Pipette
• Test tubes

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Instructions

1. • 1

     Add 2 to 3 ml of the acid solutions to two test tubes.

   • 2

     Fill a pipette with the solution of silver nitrate.

   • 3

     Add five drops of the silver nitrate solution from the pipette to the acid in each test tube. Observe the solution in each test tube. A white precipitate will form in the test tube that contains hydrochloric acid. The solution in the other will remain clear, indicating for hydrofluoric acid.