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The Ammonia Fountain

The Ammonia Fountain. When a few drops of water are added to ammonia gas in an inverted florence flask, the vacuum is filled with water and the water changes color. Purpose. To see what happens when ammonia gas reacts with a small amount of water To observe the color change of litmus

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The Ammonia Fountain

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  1. The Ammonia Fountain When a few drops of water are added to ammonia gas in an inverted florence flask, the vacuum is filled with water and the water changes color

  2. Purpose • To see what happens when ammonia gas reacts with a small amount of water • To observe the color change of litmus • To demonstrate how a partial vacuum is formed and filled

  3. Demonstration • Ammonia gas was in the florence flask • When a few drops of water were added to the flask, the ammonia completely reacted with the water • A partial vacuum was produced in the flask • Water with indicator rushed from the beaker into the flask and changed to purple

  4. Concepts 1. Equilibrium Reaction 2. Partial Vacuum 3. Indicators

  5. 1. Equilibrium Reaction • Ammonia gas reacts with water NH3(g) + H2O(l) NH4+(aq) + OH-(aq) • When ammonia reacts with water there are four “species” formed since this is an equilibrium reaction • Hydroxide ion makes the water “basic” ammonia ammonium ion hydroxide ion water

  6. 2. Bases • A base is defined as a substance that produces hydroxide ion when dissolved in water • Ammonia produces hydroxide ion in water • Ammonia is therefore a base

  7. 3. Indicators • Indicators are substances which change color in acids or bases • Litmus is a common indicator • Litmus is orange in acid when in water but purple in bases

  8. Conclusions • The gas in the florence flask filled it completely, but all the gas dissolved and reacted in just a few drops of water • When the gas reacted in the water, water rushed in to fill the space it originally occupied

  9. Comments (I) • There are many classic fountain demonstrations commonly performed • Instead of ammonia, hydrogen chloride or other water-soluble gas could be used

  10. Comments (II) • A base is a substance that produces hydroxide ions when dissolved in water • A acid may be thought of as the opposite of a base: an acid produces hydrogen ions when dissolved in water • Hydroxide ions will react with hydrogen ions to produce water OH- + H+ H2O

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