Ammonia (1959)

[Music] this film will concern itself with the  chemistry of ammonia and H3 and its Solutions in water known as ammonia water or ammonium  hydroxide solution we will study the laboratory preparation of ammonia gas its reactions  under several different circumstances and also the reactions of its solution in water  in the course of our experiments on ammonia we will need to identify the gas from time  to time and therefore we need to develop a quick test for its presence ammonia dissolves  in water to give Solutions which are uh rather weakly basic and therefore the most convenient  and most rapid test for the presence of ammonia depends on this property since ammonia is the  only common gas encountered in the inorganic laboratory which is basic in this tube we  have some distilled water containing a a drop of methyl red indicat and in this tube water  containing some pheno phine indicat to this tube also I've added one drop of hydrochloric acid  so that the indicator is now exhibiting its red or acid color now to each tube I'll add a  few milliliters of ammonia water or ammonium hydroxide you should notice that the methyl red  indicator changed from red to yellow and the phalan indicator changed from colorless to  its characteristic pinkish red color in basic solution now either of these indicators uh can  be used to test for the presence of ammonia and we will use them from time to time in the course  of the forthcoming experiment ammonia gas can be conveniently generated in the laboratory from  ammonium salts or Solutions of ammonium salts and strong bases such as sodium hydroxide the  hydroxide ion reacts with the ammonium ion with the production of water and NH3 which can be  expelled from the solution in this test tube I've placed about this much ammonium chloride  solution and about this much sodium hydroxide solution in this tube we have some distilled water  containing phal any evolved gas will pass through the delivery tube and down near the surface  of this solution and since ammonia is soluble in water water if any ammonia is formed it will  dissolve in the solution producing a color change we will now heat the contents of the large test  tube and observe what happens in the small test tube the mixture of ammonium chloride and  sodium hydroxide is boiling in the large tube the gas is passing over this gas is a  mixture of water vapor and ammonia the water vapor condenses in the cold tube reducing the  liquid that you see but it's obvious that ammonia is being evolved from the solution also because  it is colored the phenos saline in a small test tube uh a bright pink red color characteristic  of this indicator in Solutions of ammonia and water it's also possible to generate ammonia  from a solid ammonium salt and a solid base in the test tube we've placed a mixture of  ammonium sulfate and calcium hydroxide both solids which have been ground together in the  small mortar we'll now heat these uh two salts and again observe the reaction of the evolved  gas with the phenalene solution in the small test tube we're now heating the mixture of the  solid ammonium sulfate and calcium hydroxide and the produced gases are being liberated near  the surface of the phenalene solution in the tube which you see I'll now insert a stirring  rod and mix it's obvious that ammonia gas has been evolved dissolved in the water and changed  the color of the phthalan indicator we tested Solutions of ammonium hydroxide with methyl red  indicator and with phine and we found that they tested uh basic now the cause uh for this  test was the hydroxide ion and it used to be thought that this hydroxide ion was produced  by the dissociation of the molecule of ammonium hydroxide more recently however uh chemists have  decided that there is really little evidence for the existence of this molecule at all and  that this equation is preferred this shows the molecule of ammonia reacting with water  reversibly to form some ammonium ions and some hydroxide ions the uh practice of referring  to Solutions of ammonia in water as ammonium hydroxide still persists however even though  this equation this probably the more accurate representation of what is taking place in any case  the hydroxide is present and causes Solutions of ammonia to act as a base we then found that when  we reacted ammonium chloride Solutions with sodium hydroxide Solutions ammonia was liberated and  the other products of the reaction were water and sodium chloride then we found that when  solid ammonium sulfate was heated with calcium hydroxide again ammonium was liberated along  with water and calcium sulfate remained in the tube we are now utilizing the principles  Illustrated in the preceding experiment for the production of ammonia gas uh in  some quantity for laboratory use in the flask we placed a mixture of ammonium sulfate  and calcium hydroxide we're heating this with the bunson burner NH3 will be evolved pass  through this glass tube up into into the bottle since ammonia is considerably lighter  than air having a weight of 17 on the scale or a is about 29 we're collecting this gas by  the downward displacement of air we'll collect several bottles of ammonia in this way and  then uh use them to examine several different chemical properties of ammonia previously  the statement has been made that ammonia is quite soluble in water to illustrate this  point I'll place a bottle of the ammonia that we've just collected in this Beaker the water  in the beaker contains some phening that we've added you see that the water is rapidly  rising in the bottle indicating the speed with which ammonia dissolved you see also  that this water has turned red once again indicating ammonia's properties as a base next  we will test the ability of ammonia to burn in air and to support combustion the bottle contains  ammonia which we produced from our generator with this splint I'll invert the bottle bring  the splint to the mouth you notice that nothing much seems to happen when the splint  is lowered into the bottle it is extinguished this test indicates that ammonia does not burn  in air and that it does not support combustion the bottle on the stand contains ammonia which we  prepared in our generator in another bottle I have pure oxygen gas I'll invert the ammonia bottle and  place the bottle of oxygen mouth to mouth with it we'll permit the bottles to stand in this position  for several minutes and will then attempt to light the mixture we'll now remove the top bottle and  attempt to light the gas in the bottom bottle we now attempt to light the gas in the  top bottle both times a puff of flame was obtained indicating that while  ammonia won't burn in air it will burn in a mixture of ammonia and oxygen the  gases that are produced are water vapor and nitrogen a characteristic reaction of ammonia is  its reaction with hydrogen chloride to produce the salt ammonium chloride in this bottle  we have some ammonia which we made with our generator on this filter paper I've placed  several drops of a solution of concentrated hydrochloric acid I'll now drop the filter  paper with the acid on it into the bottle of ammonia you see that the bottle rapidly fills with  dense white fumes of ammonium chloride the ammonia we produced in our generator was tested with  a flaming splint and we found that the ammonia neither burned nor supported combustion under the  conditions of this experiment this indicates that ammonia and oxygen then do not react under these  conditions a mixture of ammonia and pure oxygen can be made to react with the production of  nitrogen and at higher temperatures elements react with the formation of nitric oxide our  result though is the one obtained at essentially room temperature with air as a source of oxygen  we can say that a mixture of hydrochloric acid Vapors and ammonia react rapidly and vigorously  with the production of ammonium chloride salt we will now examine the use of a solution  of ammonia in water or ammonium hydroxide as a precipitating agent in the two test tubes  I've placed small samples of magnesium chloride solution and feric chloride solution which I  diluted with a few milliliters of distilled water we'll now add a small quantity of ammonium  hydroxide solution to each tube and examine the results in each tube a precipitate has has appeared in the  tube on the left we have the white precipitate of magnesium hydroxide and in the tube on the  right the reddish brown precipitate of feric hydroxide obviously then ammonia water contains a  sufficient concentration of hydroxide ion so that the solubility products of both magnesium  hydroxide and feric hydroxide have been exceeded before we saw that the addition of  ammonia water to Solutions of feric chloride and magnesium chloride caused the precipitate  of the respective hydroxides to be obtained in each case now in the two test tubes we've can  place Solutions of magnesium chloride and feric chloride this time however to each tube I'm going  to add a rather large amount of ammonium chloride solution and then proceed to add some ammonium hydroxide and you'll notice an immediate difference in the  appearance of the material in the two tubes feric hydroxide is still precipitated by the ammonia  water we can see the copious precipitate here while magnesium hydroxide is not obtained in  this case this result is obtained because the presence of large amounts of ammonium ion from  the ammonium Chlor repress the ionization of the ammonium hydroxide and greatly reduce  the concentration of hydroxide ion when we added a solution of ammonia water to Solutions of  magnesium chloride feric chloride the precipitate of the hydroxides was obtained in each case  because the concentration of hydroxide ion produced by the ionization of the ammonia uh  gave us sufficient hydroxide ion concentration to C the product of the magnesium ion and the  hydroxide ion squares to exceed the solubility product for magnesium hydroxide and similarly  for feric hydroxide and precipitates of these two hydroxides were obtained when ammonium  chloride was present in the solution this High concentration of ammonium ion due to the ammonium  chloride caused this equilibrium to reverse to the left and made the concentration of hydroxide  ion very small and this smaller concentration of hydroxide ion 1 squar and multiplied by the  magnesium ion must now have been less than the solubility product for magnesium hydroxide  because no precipitate was obtained however feric hydroxide is so insoluble or its solubility  product constant is so small that even the greatly reduced hydroxide ion concentration present  when cubed and multiplied by the feric ion concentration exceeded the solubility product  constant for feric hydroxide we've seen that ammonium chloride ammonia water mixtures then  can be used to separate mixtures of the magnesium ion and the feric because uh the magnesium ion  will remain in solution while a ferak will be precipitated out as the hydroxide this experiment  also illustrates that these insoluble hydroxides such as magnesium hydroxide and feric hydroxide  still differ greatly in solubility because we've demonstrated here that magnesium hydroxide  must be considerably more soluble than feric hydroxide finally in our study of ammonia water  as a precipitant we'll examine its reaction with copper sulfate solution in the test tube I placed  about 1 ml of copper sulfate solution and about 5 m of water and to this solution I'm going  to add ammonium Hydro oxide or ammonia water dropwise you'll see that the first  drop of ammonium hydroxide causes the formation of a whitish  precipitate this is copper hydroxide with additional drops of ammonia water more and more precipitate is obtained  now as we continue to add ammonia water you'll notice that the precipitate in this  region of the tube is disappearing and the deep blue color which is characteristic  of the copper ammonia complex ion is appearing in the tube we now have a mixture  of copper hydroxide and some copper ammonia complex ion and by adding several more drops of  ammonia water we can cause all the precipitate to dissolve which it is now done we see  therefore that when ammonium hydroxide is added to copper sulfate Solutions a precipitate of copper hydroxide is first obtained  and then as more ammonia is added this precipitate dissolves we'll examine the  equations for this reaction in the next sequence when we added dropwise ammonia water  to solution containing the copper ion we found that the first thing that happened was that  we obtained a precipitate of copper hydroxide this precipitate was formed because of the  hydroxide ions produced by the uh ammonia water reacting with the copper ion forming  copper hydroxide and this occurred because concentration of copper ion times hydroxide  ion squared was greater than the salability product constant for copper hydroxide this was  a situation when we added just a few drops of ammonia water you should bear in mind that some  copper ions are always present in solution in equilibrium with the copper hydroxide precipitate  then we added considerably more ammonia water and when this was done the ammonia molecule  present reacted with those few copper ions which were in equilibrium with precipitate  converting these copper ions to The Copper ammonia complex ion now it's copper ions were  removed from this equilibrium and converted to The Copper ammonia complex the precipitate of  copper hydroxide dissolved because the copper ion concentration became so small that now  this reduced copper ion concentration times the hydroxide ion concentration squared was less  than the cability product for copper hydroxide by adding a sufficient quantity of ammonia  water we eventually converted nearly all of the copper ions to Copper ammonia complex ions  and dissolve the precipitate completely [Music]