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Published byAsher Sherwin Modified over 3 years ago
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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 The Ammonia Fountain
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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
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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
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Concepts 1.Equilibrium Reaction 2.Partial Vacuum 3.Indicators
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1.Equilibrium Reaction Ammonia gas reacts with water NH 3 (g) + H 2 O(l) NH 4 + (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” ammoniaammonium ion water hydroxide ion
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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
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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
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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
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Comments (I) There are many classic fountain demonstrations commonly performed Instead of ammonia, hydrogen chloride or other water-soluble gas could be used
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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 + H 2 O
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