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The Acidic/Basic Nature of Anhydrides and Salts

As a way to visualize how substances other than acids and bases can have acidic and basic properties, we placed some litmus solution in various aqueous solutions.  Pictured below is how the litmus looked in distilled water, hydrochloric acid, and sodium hydroxide.  Notice the light purplish color in the water, the light pink/peach color in the hydrochloric acid, and the deep purple color in the sodium hydroxide.  

H2O                HCl                 NaOH

Pictured below are two solutions representing the anhydrides.  The one on the left was formed by blowing bubbles in the solution.  The pink color is due to carbon dioxide, an acidic anhydride.  The flask on the right, contains CaO (commonly known as lime) and is a deep color due to the basic nature of the basic anhydride CaO.  

CO2                  CaO

The final image below shows how salts can have varying acid/base natures.  Notice the NaCl is the same light purplish color that the distilled water is, indicating that NaCl is a neutral salt.  The NaHCO3 (baking soda) and the NaC2H3O2 are the same deep purple color that sodium hydroxide is, indicating their basic nature.  Notice the litmus reveals that the other salt, the NH4Cl (smelling salt) is an acidic salt.

NaCl    NaHCO3        NH4Cl    NaC2H3O2


D.C. Everest Senior High
6500 Alderson Street
Weston, WI 54476

Bill Heeren, Teacher
November 16, 2013

Phone (715) 359-6561
Extension 4204
Fax (715) 355-7220