Sulfuric Acid (1960)

[Music] thank you [Music] we are going to study the properties both physical and chemical of sulfuric acid or hydrogen sulfate as you can see from the contents of this bottle this material is a colorless liquid we're going to study its viscosity and several types of chemical reactions which it undergoes in particular we're going to study effectivity as an acid its activity as an oxidizing agent and its activity as a dehydrating agent in these two 10 milliliter pipettes we've placed in the pipette on the right from sulfuric acid concentrated and in the pipe pad on the left water the rate at which these two liquids drain from these pipettes will be a rough measure of the relative viscosity of the two liquids I've previously established that water drains from each of these pipettes at about the same rate the liquids are now draining from both pipettes and you'll notice that the water on the left is draining out at about twice the rate of the acid on the right this indicates an accrued way that the viscosity of sulfuric acid is about twice that of water sulfuric acid and water mix in all proportions but in the process of mixing considerable heat has evolved in this Beaker I placed about 50 milliliters of cold water and in the graduated cylinder we have 50 milliliters of concentrated sulfuric acid I'll now add the acid to the water in the beaker and you should note the rapid change in temperature which takes place before we added sulfuric acid to water and found that although a great deal of heat was evolved the reaction was fairly gentle that is no spattering took place now in this sequence we'll demonstrate the incorrect way to mix sulfuric acid and water in the beaker I placed 50 milliliters of sulfuric acid from the bottle and in the graduated cylinder we have 50 milliliters of water I'll now add the water to the acid and you should note the more violent effect of the mixing than was true before we turn now to a consideration of the properties of solutions of hydrogen sulfate as an acid in this tube I've placed some sodium hydroxide solution a little distilled water and a few drops of methyl red indicator the indicator has assumed the yellow color which is characteristic of it in basic solution in the center tube I've placed a small quantity of sodium carbonate and in this tube few pieces of ferrous sulfide I'll now add a few milliliters of dilute sulfuric acid to each two you should note that the indicator change from its basic or yellow color to its red or acid color indicating if the sulfuric acid neutralized the sodium hydroxide sodium carbonate reacted with effervescence CO2 gas was produced the lead sulfide and the sulfuric acid are reacting with the production of the gas this gas should be hydrogen sulfide we'll test the gas with a strip of lead acetate paper our regular test for hydrogen sulfide we notice that the the lead acetate paper turns brown or black indicating that hydrogen sulfide is produced when lead sulfide reacts with sulfuric acid in each of these three cases then sulfuric acid has behaved as a typical acid the reaction about to be carried out is one that you have seen before but it illustrates the general property of sulfuric acid so we will repeat it here in the test tube I placed some crystals of sodium chloride and to these crystals We'll add a few milliliters of concentrated sulfuric acid reactions start promptly and you know from your previous experience that the gas being produced is hydrogen chloride I believe you can see some fumes rising from the mouth of the test tube where the hydrogen chloride is coming in contact with the moist air in the room this reaction of sulfuric acid with salt is characteristic of most high boiling acids the acid form in this case hydrogen chloride is produced we've noticed however that sulfuric acid is a pretty good oxidizing agent so this method can only be used when the acid produced in this case hydrogen chloride is resistant to oxidation the equations on the board illustrate three reactions of the loop sulfuric acid acting as an acid in the first equation the glute sulfuric acid neutralized sodium hydroxide producing salt sodium sulfate and water in the second reaction sulfuric acid reacted with sodium carbonate producing again sodium sulfate and liberating carbon dioxide and water the third equation blue sulfuric acid reacted with ferrous sulfide producing ferrous sulfate and hydrogen sulfide here we show the reaction between concentrated sulfuric acid this time and sodium chloride the product being sodium hydrogen sulfate and hydrogen chloride which was evolved we will now consider the activity of concentrated sulfuric acid as an oxidizing agent again we're going to use two reactions that you've seen before which illustrate the activity of sulfuric acid in this respect very nicely in this test tube I've placed several crystals of potassium bromide and in this tube potassium iodide I'll now add a few milliliters of concentrated sulfuric acid to each two in this tube you should observe the reddish yellowish color produced by free bromine and this tube the brown color characteristic of iodine this tube is also liberating hydrogen sulfide gas as we demonstrated earlier we will now uh study the difference in the reactions with metallic copper when we use concentrated sulfuric acid and dilute sulfuric acid in each of these test tubes I've placed some copper metal turnings to this tube I'll add some dilute sulfuric acid and to the other two and concentrate itself here again we'll now heat both tubes with the Bunsen burner for a few moments a few minutes later the tubes now have this appearance the dilute sulfuric acid and the copper do not appear to have reacted at all and indeed this is the case dilute sulfuric acid is not a strong oxidizing agent obviously not strong enough to attack copper on the other hand in the tube containing the concentrated sulfuric acid there is obvious evidence of a reaction we'll now let this tube cool to room temperature and then pour its contents into some cold distilled water the tube containing the concentrated sulfuric acid and copper mixture has been placed in this Beaker of cold water and permitted to cool I'll now pour the mixture into the small Beaker containing some distilled water and will now filter this reaction mixture first I'll pour a little bit of the liquid back into the copper sulfuric acid reaction tube and rinse off the remaining copper we'll now filter this reaction mixture the filtrate has this appearance you'll notice the characteristic blue color of the hydrated copper eye the anion can only be the sulfate ion but we can confidently assume that the reaction of sulfuric acid concentrated with metallic copper produces copper sulfate as one of the products during the reaction the odor of sulfur dioxide was present at the mouth of the tube this indicates that the reduction product of the sulfuric acid was sulfur dioxide when we place concentrated sulfuric acid on potassium bromide the first reaction to take place liberated some hydrogen bromide within hydrogen bromide reacted at least in part with more of the concentrated sulfuric acid reducing the sulfuric acid to sulfur dioxide the hbr was oxidized to bromine this illustrates sulfuric acid acting as an oxidizing agent when the reduction product is sulfur dioxide and when we use potassium iodide and concentrated sulfuric acid the initial product was hydrogen iodide which reacted with excess sulfuric acid to produce iodine and hydrogen sulfide well this equation illustrates a second reaction of concentrated sulfuric acid as an oxidizing agent in this case its reduction to hydrogen sulfide and from these two equations we can see that hi is a better reducing agent than hbr then we reactant concentrated sulfuric acid with copper and we found that the products for the reaction for copper sulfate and sulfur dioxide and water so this illustrates another reaction of concentrated sulfuric acid as an oxidizing agent when the reduction product is sulfur dioxin the third property of sulfuric acid to be Illustrated is its activity as a dehydrating agent in this beaker I placed about 100 cubic centimeters of cane sugar or sucrose in the beaker I have 100 milliliters of sulfuric acid which has been heated to about 70 degrees Centigrade the reaction will take place without heating but is more rapid if warmth sulfuric acid is used I'll now pour the sulfuric acid onto the sucrose and stir sulfuric acid has reacted with the sugar abstracting the elements of water and leaving carbon behind the water formed has produced Steam and the steam has inflated the carbon so that a mass of carbon and sulfuric acid and pushed by the steam has risen out of the beaker on the tripod I've placed a piece of ordinary cotton cloth and onto this cloth I'm going to pour a few drops of hot concentrated sulfuric acid now as before the reaction will take place with cold sulfuric acid but heating or reacid speeds up the rate of reaction you can observe that the cloth is very rapidly attacked and that it disintegrates a hot concentrated sulfuric acid attacks clothing in the same way and also devours flesh does it cheerfully as it does cloth so that when you're working with this chemical great precaution should be taken to keep it off of your skin when sulfuric acid was used as a dehydrating agent we studied its reaction with sucrose or sugar which has the formula C12 h22o11 this compound contains hydrogen and oxygen in the same proportions as they occur in water and we saw that the reaction which resulted produced carbon and water sulfuric acid acting to abstract the water from the sucrose the large mass of carbon that resulted was inflated by the steam produced and Rose from the beaker when the sulfuric acid reacted with cloth a reaction similar to this took place because the cellulose and cotton cloth are the formula very similar to that of sugar although somewhat more complicated the overall reaction is much of the same type however foreign