in this lab we will be studying a chemical reaction at equilibrium between two complex ion formations of cobalt because they form complex ions with water and or chloride ions very favorably we can see which side of the reaction is favored by the color changes due to Crystal field Theory which is not part of this um lab but we're going to be studying later's PR ible and noticing at equilibrium if a stress is made and let's say a stress is made that forces the reaction to go thermodynamically to the right we should be able to see a nice blue color because the reactants get used up and will make more products which will be of course that complex with the chloride iion as chloride with that ligan and of course back at equilibrium if we do something that favors the reverse um reaction where we're going to make more of the um Red by using up the reactants and we will make more of the Cobalt complex that has the water surrounding it as the ligan which will be red we can observe these shifts in equilibrium so let's get started so just to show you uh this is the color or Baseline colors of the Cobalt complex with water and this is the color nice blue color of the Cobalt complex uh with the chloride ion so clearly you can see who's favored and by looking at these colors and this is I believe a purple color although I have difficult time with colors of the equilibrium mixture of both all right so we're going to put out some test tubes here and we're going to follow our procedure as follows so here's our four test tubes and again right now we see the pink color so all these test tubes currently have a lot more of the reactants and products as by the uh pink color favoring the Copp complex with water so we're going to Vin our first test and we're going to just uh add some hydrochloric acid into the first test tube and doing so we see that thermodynamically there is a shift from this reaction going to the side with the blue compound so now we're making a lot more cobalt chloride complex the complex that is blue okay and and very clearly you should be able to figure out in your lab who is being used up and who's being [Music] increased all right so in test tube two we're going to add some calcium chloride and we'll add some more and we should be looking at the bottom of the test tube and the calcium chloride is going to dissociate into its ion that's important you understand into the calcium plus two and the chloride negative ions all right calcium is a salt all right and as I probably bring this closer to us we can see that the bottom of the test tube show shows a favored thermodynamic pathway meaning we see a shift toward the blue side we are making a lot more of that Cobalt ion complex with the chloride ion so clearly you are now shifting one way now of course there's not enough chloride ions to make full test tube go but right where the salt is you can clearly see there is some shift that favors the formation of the blue complex and you should be able to know which side was shifting and in your lab or which reactants and products are going up or going down because of that all right so that's one and two test now we're going to grab test two number one again and we're going to do another test here at some point all right so here comes test tube one again which we can see is clearly favored all right with the blue compound all right and uh now we're going to add some water all right so now adding some Poland Spring water and again this is not a uh uh they didn't pay us any money to do this but we're going to add some water and by adding water you can see definitely a shift toward the pink uh Cobalt complex and that pink Cobalt complex um is on the reactant side so again you should be able to figure out where the reaction is Shifting to by uh whether we making a pink or blue complex here all right and again these colors are due to Crystal field Theory where we're drawing in the lians okay into the D's orbitals and causing the D's to split pretty cool stuff to go through so test tube three here okay we're going to add hydrochloric acid which we've done already before and we're going to see a shift um to that favors um the cobalt chloride complex and you should know what that shift does and now part of the same test now is we're going to add some silver nitrate notice the silver nitrate bottle when it comes into play here has a is a um dark bottle that prevents uh light from getting in too much cuz the silver iron are affected by the Light any case you see me adding some silver nitrate and clearly I see some solid developing as we like to call a precipitate and that precipitate is building up as I add more silver nitrate and I also see a color change here okay as I keep adding more silver nitrate I see it going from this blue complex back to the pink side so I definitely see a pink color developing here as we add some silver nitrate so probably going to bring this up to you and see up close and personal what this looks like and there she is and you can see the solid on the bottom the solid definitely has a white color okay but that's not what's affecting the color this definitely went pink showing us a definite shift in equilibrium to the um Cobalt complex that has a pink color and you should make the appropriate markings in your lamp something about making this precipitate cause the shift to favor the formation of the um reactants the original reactants something to think about there what did we do there that caused that reaction to shift to the uh side that produced the pink complex silver nitrate H we should know about the uh solubility PR uh rules of solubility and what the silver ion must have done okay so our final test now is to put our test Tu 4 which is favoring the pink side and I'm bringing a thermo um an infrared thermometer to show you that the um room or the board behind you is 25.5 de C and the and the water I'm bringing here is 76° C so I'm going to use a hot bath and in this test we're going to put the test tube four in the hot bath and we're going to see what kind of color change will happen now we're changing the temperature here so we're actually going to shift not so much the equilibrium in truth we're actually changing the equilibrium position to favor one side or the other by adding heat okay we are definitely Shifting the equilibrium to a new position that's favoring if you can see the blue Co cobalt chloride complex all right and that tells you something about where the heat is you know something about L sher's principle you increase the temperature the reaction is going to shift to always do the opposite it's response is opposite so looks like it's shifting in response increasing the temperature which means it's trying to probably relieve that temperature and this should tell you where the heat is in this reaction okay is the heat go on the reactant side or the product side one of the questions in the lab okay is to find out whether the board reaction is endo and EXO and right here these tests are telling you all right so in my second test I'm going to add a cold water bath and this test should also support my understanding uh so here I have my U infrared thermometer I get about 9° of my ice bath here and I put my my warm solution back into the ice bath and we can probably guess what's going to happen here and lowering the temperature the reaction's going to shift to do the opposite probably to to um increase the temperature so it's going to favor whatever shift of equilibrium that favors um the increase in temperature or the exothermic way you should know decrease in the temperature is the stress the reaction is going to changes equilibrium to to do the opposite and that hint of what's Happening Here should tell you from the ice bath test and the um hot bath test where the heat goes in the reaction side is the forward reaction EXO or is the forward reaction Endo all right and we can clearly see that the cold water bath made uh and shifted the equilibrium to favor the red complex all right and that's essentially this lab from these uh tests independent tests you should have be able to figure out where the shifts have occurred and who's increasing and decreasing and definitely whether the forward reaction is endo or EXO thermic all the players involved are taking their bows here I guess I left the water out hope this helped [Music]