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GIVE REASONS FOR THE FOLLOWING OBSERVATION: THE pH OF AMMONIUM HYDROXIDE DECREASES...

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reenakinshuk | Student, Grade 10 | Salutatorian

Posted December 23, 2012 at 5:48 PM via web

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GIVE REASONS FOR THE FOLLOWING OBSERVATION:

THE pH OF AMMONIUM HYDROXIDE DECREASES WITH THE ADDITION OF AMMONIUM CHLORIDE TO IT.

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ncchemist | eNotes Employee

Posted December 23, 2012 at 7:33 PM (Answer #1)

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Let's look at pH and the two chemicals in question.  pH is a measure of the acidity (proton concentration) of a solution.  Acidic solutions are lower in pH and basic solutions are higher in pH.  Ammonium hydroxide is NH4OH.  It can be thought of as a solution of ammonia (NH3) in water (H2O).  Ammonia is a weak base.  As a result, ammonium hydroxide is a basic a chemical and will have a pH greater than 7.  Ammonium chlorde (NH4Cl) can be thought of as a mixture of ammonia and HCl.  HCl is a very stron acid, so NH4Cl is acidic and a mild source of protons.  So if NH4Cl is added to NH4OH, the pH of the solution will go from a higher number (basic) to a lower number (acidic).  This accounts for the observation.

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