There are test tubes with dry substances: in one – ammonium sulfate, in the second

There are test tubes with dry substances: in one – ammonium sulfate, in the second – sodium sulfate. Determine which test tube contains ammonium sulfate.

To determine which test tube contains ammonium sulfate, it is necessary to carry out a qualitative reaction for the ammonium ion. To do this, add an alkali solution, for example sodium hydroxide, to both test tubes, and heat both test tubes.

In a test tube with ammonium sulfate, as a result of the reaction, ammonium hydroxide is formed, which, when heated, decomposes into water and ammonia. Ammonia is released from the heated solution and is determined either by smell or by means of litmus paper moistened with water over the test tube. It should turn blue. This is due to the fact that ammonia from the air forms a compound with water – ammonium hydroxide. The alkaline ammonium hydroxide medium will turn the indicator blue.

The reaction equation can be summarized as follows:

(NH4) 2SO4 + 2 NaOH = Na2SO4 + 2 H2O + 2 NH3

There will be no ammonia odor over the sodium sulfate test tube and the litmus paper will not turn blue.