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Gas Lab Manual

2. Confirmatory Tests for Gases

c) Test for Ammonia Gas

TEST
Ammonia gas, NH3

1a) Place 2 spatula of ammonium chloride in a test tube. Add 3 cm3 dilute sodium hydroxide. Warm gently.

b) Hold a piece of moist red litmus paper over the mouth of the test tube when mixture is warmed.
Observations Pungent gas evolved turned moist red litmus blue.
Type of Chemical reaction involved to test for gas. Ammonia gas dissociates partially in water to form hydroxide ions, OH-, which turns red litmus blue.
Chemical equation NH3 (g) + H2O (l)   ----->     NH4+ (aq) + OH- (aq)

 

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