Equilibrium and Thermodynamics Experiment

Okay folks, today we're going to be learning equilibrium and thermodynamics. Then you're going to calculate enthalpy, entropy, and it gives free energy of dissolution of borax in water. So these are the class weather unit. So you need a burette. So basically that's for for titration. We have 5 ml foliometric pipette. So this is for transfer 5 ml of water to make the mark on the test tube. So you're not going to be using these. to transfer borax. Then you're going to need a digital thermometer. Okay, so make sure that you clean this before you return it to the stock room. Now, the objectives of this experiment is to tige HCl with saturated solutions of borax. So this will help us determine the value of equilibrium constant of the dissolution and then you're going to see the dependence on Ksp on temperature and then we're going to use a plot of Ksp and temperature to calculate delta H, delta S, and delta G for the dissolution. So this is the overall equation of the equilibrium. So you dissolve sodium theta borate to form these ions. So we see that from this equation, you can see that for every ion of borate, we form two ions of sodium. So we can replace that in case P expression as shown here. Instead of using sodium, I'm going to use two ions of borate. Now, we're going to titrate the basic solution of borax, borate, with the acid to form this acidic solution. So, at each temperature, the relationship between Gibbs free energy temperature and Ksp is given here. So, we have these two equations. Now, when you combine these two equations and make ln of Ksp, the sub-decalc formula you get this equation here. So when you plot ln of ksp versus 1 over t, you get a straight line whereby the edge of r as a slope and delta s of r as the intercept. We have here r as a constant. Now for the first part of this experiment we have to prepare test tubes, 10 of them. So two at each temperature. As I said before we're not going to use pipettes to dispense 5 ml of borax. So instead you're going to use the pipers to get 5 ml of water and make a mark on the test tubes. Each of the test tubes at 45 degrees has this mark here. So for this experiment equilibrium and thermodynamics, so for the procedure you have to make six test tubes, ten test tubes. For the preparation of test tubes, you're going to get 5 ml of PI water and make marks like that. So we're not going to be using UDS to transfer our borax. Now, once you have all the test tubes, we have 10 test tubes in total. So we're going to be preparing a saturated borax solution. So the second part of the experiment is preparation of saturated borax solution. In a 2-mL beaker. you get about 30 grams of borax and then you add 150 ml of water and then you're going to warm the mixture to a temperature not higher than 50 degrees celsius anything above that borax will start to compost all the 30 grams of borax dissolves you can add a little bit more borax until excess solid is present in solution so that ensures that the solution is truly saturated so here i have 30 grams of borax solution in 150 ml of DI water. So I heated this to about 50 degrees while stirring it, and the solution should be super circulated. So after dissolving the 30 grams, I added more. borax to make sure that it is saturated. So I have that there. So you make sure that the temperature does not exceed 50 degrees because that will lead to decomposition of borax. The third part of this experiment is sampling of saturated borax solution. And you have to do this really carefully, and this is where you need to be careful. So you're going to let the solution cool to about 45 degrees Celsius. gonna measure the temperature okay in the beaker and then you're gonna pour directly like this five ml of the thorax without the solid into one of the test tubes at 45 degrees celsius then you're gonna measure the temperature of the beaker that's after you dispense five ml then you're gonna do the same thing for the other test tube at 45 degrees celsius remember you have two test tubes at the temperature You measure the temperature of the solution, dispense 5 ml into the second test tube, and then measure the temperature of the solution in the beaker. So you're going to repeat the sampling for the test tubes at 5, 285, 15, and 5 degrees Celsius. So you might have to use an ice bath to cool the test tubes to negative 15 and 5 degrees Celsius. So you're going to cool the beaker here to ensure that the solution is at 15 and 5 degrees Celsius. Do not use the pipette or the funnel to transfer the solution. Now when you're transferring the solution, you're going to let the solid settle for a little bit so that you are not transferring the solid substance. When it comes to sampling of the solution, so here we have to maintain a good temperature. So we're going to take the temperature of the solution before you transfer. and the temperature of the solution after you transfer. So I'm going to do one demonstration here at 45 degrees. So we really know that the temperature here of the borax is about 45 degrees Celsius. Let's see right now. Alright, that's good. So I know that computer. So I'm going to transfer the solution to a 50mm. Let me settle first for a few, briefly. So we want to make sure that we are not transferring the solid into the beakers. So I have this. The temperature, I record that. Make sure that the storm is the same temperature here. Then, last for this tip number one. Five degrees. For the next four, five degrees, I'm gonna do the same thing. Okay. The arms. temperature So now I have test tubes at 45 to research it for each test tube Each pair of test tube at 45 or 35 25 and the rest of the temperatures you're going to titrate the borax with hcl so you're going to prepare burette as always the hcl is going to go to the burette clamp it make sure that you remove the air bubble you're going to get this um the solution the solution saturation borax solution at 45 degrees celsius let it dissolve at temperatures at temperatures less than 50 degrees celsius so the solution is already saturated so measure All you have to do is to make sure that you dissolve it. But when you're titrating, you don't have to dissolve it. You might have to add sufficient warm water to re-dissolve the borax at room temperature. Now you can add two to three drops of bromocresol green. So bromocresol green, when you start the experiment, is blue. That's in basic solution. The endpoint is where the solution turns yellow. Bromocresol green is yellow in acidic. So now I want to transfer this Because the next step is titration. So I'm going to transfer these solutions to an alum-myoflask. So to transfer these solutions, I have two solutions, two DI waters. So we have one DI water for rinsing and one DI water for dissolving, to dissolve in the borax solution. So distribution, DI water, he asked for 5 degrees Celsius. So I'm going to add a little bit of warm PI water. As you can see there is a little bit of borax crashing out. I might need to uh, start this. So I have this 100 mile thrust. Transplant that. Down here, we have this DI water for rinsing. This DI water is at 45 degrees again. The entrance down there. I'm going to add enough warm water to dissolve the borax. As you can see, all the borax is dissolved. So I'm going to add the indicator here. I'm going to add three drops of the indicator. So the indicator is blue in basic solution and yellow in acidic. So starting point is going to be blue. All right. So that's ready. Now I'm going to prepare the burette with the acid. So here I have HCL, 2-0 molar HCL. And I'm going to use the titrate with the HCL. With the borax. So I'm going to put a little bit of borax in there. Make sure that I rinse that. And this all solutions can go down the same way. Okay. So I'm going to fill this one up here with the . So I'm going to follow the same procedure. So remove the bubble. So we follow the same procedure. We are going to read the initial volume of the puree. So right now it's at 1.40. Again, we're going to measure the volume to 0.01. Alright, so now I'm ready for titrate. I have HCl, I have borax. Initial color is blue, so we want that yellow color. That's an acidic solution. So again you want that persistent yellow color. As you can see I'm still adding, going a little fast at the beginning. So as you get closer to the endpoint, you see a yellow color where the acid touches the solution. So we still have the, so as you can see the solution is no longer white, white blue. So that's the color that you want. So that means that that's the end point. Alright, so again you want to be careful that you can't close the envelope so that you don't overshoot the envelope. Alright, so for the other reactions we have test tubes at different temperatures. So we have to do at 45 degrees, have the same titration at 45 degrees, and average the volume. You're going to find that the volumes of the acid used are two different temperatures. Now, so you have to do this five times, twice at each temperature, so the role of 10 titrations. Okay? Your first data set should look like this. You have the volume of HCl that you use to titrate with the borax. You have temperatures for each pair. For the five degrees, you have two volumes. Then you're going to calculate the moles of borax that was present in the saturated solution using this equation. So remember the equation for titration. You have one mole of borax equivalent to two moles of borax. So you're going to use that equation to calculate the moles of borax. And then you're going to use equation 3 to calculate Ksp and then find ln of Ksp. So once you have the ln of Ksp, you're going to plot that against 1 over T. That should give you a straight line with an intercept and a slope. So the slope will be negative delta H over R. The intercept will be delta S over R. Slope will be negative delta H over R. You can calculate delta H and the Y intercept. is delta s over r then you're going to use that to calculate delta s you have to calculate the delta g so there are two ways two methods of finding finding delta g so you can use this equation here RT ln of ksp at each temperature or the second method you can use delta g equal to delta h minus T Delta S. So these values you calculate from the previous slide. So you have to do both of these methods for this experiment. Now when you have both Delta G at using the two methods, so you can upload Delta G as a temperature in one graph. The critical parts of this experiment is temperature control and transferring the solution. Make sure that you are not transferring the solid. Some things to remember. is if your solution temperature is changing rapidly and you get an accurate temperature reading so think about that if you pour a saturated solution at 45 degrees into a test tube which is called at 20 degrees Celsius what's going to happen? so that's something to think about something else to think about is once the saturation of the saturated solution is in a test tube it doesn't matter how much water you use to get it back out and heat it to alumite flask for titration don't forget to record temperature to nearest 0.1 degree Celsius, average temperatures before and after sampling, mix the solution as well to ensure that you get to equilibrium. So the water bar should not be more than 50 degrees Celsius so otherwise the borax will start decomposing. Make sure that there are no air bubbles in the burette tip and write down the concentration of standardized HCL for the calculation. So just for your information, just because delta G is positive doesn't mean things won't dissociate or dissolve for example acetic acid is a weaker acid than HCl but it dissociates in water the dissociation is not favorable it doesn't dissociate more than HCl so the lab report is as usual okay so you have to show sample calculations data tables and observations be careful with sig fix so you're going to plot delta G temperature for two methods okay and then summarize your results conclusion the discussion part and then answer these questions good luck

So you need a burette. So basically that's for for titration. We have 5 ml foliometric pipette.

So this is for transfer 5 ml of water to make the mark on the test tube. So you're not going to be using these. to transfer borax.

Then you're going to need a digital thermometer. Okay, so make sure that you clean this before you return it to the stock room. Now, the objectives of this experiment is to tige HCl with saturated solutions of borax.

So this will help us determine the value of equilibrium constant of the dissolution and then you're going to see the dependence on Ksp on temperature and then we're going to use a plot of Ksp and temperature to calculate delta H, delta S, and delta G for the dissolution. So this is the overall equation of the equilibrium. So you dissolve sodium theta borate to form these ions. So we see that from this equation, you can see that for every ion of borate, we form two ions of sodium.

So we can replace that in case P expression as shown here. Instead of using sodium, I'm going to use two ions of borate. Now, we're going to titrate the basic solution of borax, borate, with the acid to form this acidic solution.

So, at each temperature, the relationship between Gibbs free energy temperature and Ksp is given here. So, we have these two equations. Now, when you combine these two equations and make ln of Ksp, the sub-decalc formula you get this equation here.

So when you plot ln of ksp versus 1 over t, you get a straight line whereby the edge of r as a slope and delta s of r as the intercept. We have here r as a constant. Now for the first part of this experiment we have to prepare test tubes, 10 of them. So two at each temperature. As I said before we're not going to use pipettes to dispense 5 ml of borax.

So instead you're going to use the pipers to get 5 ml of water and make a mark on the test tubes. Each of the test tubes at 45 degrees has this mark here. So for this experiment equilibrium and thermodynamics, so for the procedure you have to make six test tubes, ten test tubes. For the preparation of test tubes, you're going to get 5 ml of PI water and make marks like that. So we're not going to be using UDS to transfer our borax.

Now, once you have all the test tubes, we have 10 test tubes in total. So we're going to be preparing a saturated borax solution. So the second part of the experiment is preparation of saturated borax solution.

In a 2-mL beaker. you get about 30 grams of borax and then you add 150 ml of water and then you're going to warm the mixture to a temperature not higher than 50 degrees celsius anything above that borax will start to compost all the 30 grams of borax dissolves you can add a little bit more borax until excess solid is present in solution so that ensures that the solution is truly saturated so here i have 30 grams of borax solution in 150 ml of DI water. So I heated this to about 50 degrees while stirring it, and the solution should be super circulated.

So after dissolving the 30 grams, I added more. borax to make sure that it is saturated. So I have that there.

So you make sure that the temperature does not exceed 50 degrees because that will lead to decomposition of borax. The third part of this experiment is sampling of saturated borax solution. And you have to do this really carefully, and this is where you need to be careful. So you're going to let the solution cool to about 45 degrees Celsius.

gonna measure the temperature okay in the beaker and then you're gonna pour directly like this five ml of the thorax without the solid into one of the test tubes at 45 degrees celsius then you're gonna measure the temperature of the beaker that's after you dispense five ml then you're gonna do the same thing for the other test tube at 45 degrees celsius remember you have two test tubes at the temperature You measure the temperature of the solution, dispense 5 ml into the second test tube, and then measure the temperature of the solution in the beaker. So you're going to repeat the sampling for the test tubes at 5, 285, 15, and 5 degrees Celsius. So you might have to use an ice bath to cool the test tubes to negative 15 and 5 degrees Celsius. So you're going to cool the beaker here to ensure that the solution is at 15 and 5 degrees Celsius.

Do not use the pipette or the funnel to transfer the solution. Now when you're transferring the solution, you're going to let the solid settle for a little bit so that you are not transferring the solid substance. When it comes to sampling of the solution, so here we have to maintain a good temperature.

So we're going to take the temperature of the solution before you transfer. and the temperature of the solution after you transfer. So I'm going to do one demonstration here at 45 degrees.

So we really know that the temperature here of the borax is about 45 degrees Celsius. Let's see right now. Alright, that's good. So I know that computer.

So I'm going to transfer the solution to a 50mm. Let me settle first for a few, briefly. So we want to make sure that we are not transferring the solid into the beakers. So I have this.

The temperature, I record that. Make sure that the storm is the same temperature here. Then, last for this tip number one. Five degrees. For the next four, five degrees, I'm gonna do the same thing.

Okay. The arms. temperature So now I have test tubes at 45 to research it for each test tube Each pair of test tube at 45 or 35 25 and the rest of the temperatures you're going to titrate the borax with hcl so you're going to prepare burette as always the hcl is going to go to the burette clamp it make sure that you remove the air bubble you're going to get this um the solution the solution saturation borax solution at 45 degrees celsius let it dissolve at temperatures at temperatures less than 50 degrees celsius so the solution is already saturated so measure All you have to do is to make sure that you dissolve it.

But when you're titrating, you don't have to dissolve it. You might have to add sufficient warm water to re-dissolve the borax at room temperature. Now you can add two to three drops of bromocresol green.

So bromocresol green, when you start the experiment, is blue. That's in basic solution. The endpoint is where the solution turns yellow.

Bromocresol green is yellow in acidic. So now I want to transfer this Because the next step is titration. So I'm going to transfer these solutions to an alum-myoflask. So to transfer these solutions, I have two solutions, two DI waters. So we have one DI water for rinsing and one DI water for dissolving, to dissolve in the borax solution.

So distribution, DI water, he asked for 5 degrees Celsius. So I'm going to add a little bit of warm PI water. As you can see there is a little bit of borax crashing out.

I might need to uh, start this. So I have this 100 mile thrust. Transplant that.

Down here, we have this DI water for rinsing. This DI water is at 45 degrees again. The entrance down there.

I'm going to add enough warm water to dissolve the borax. As you can see, all the borax is dissolved. So I'm going to add the indicator here.

I'm going to add three drops of the indicator. So the indicator is blue in basic solution and yellow in acidic. So starting point is going to be blue.

All right. So that's ready. Now I'm going to prepare the burette with the acid. So here I have HCL, 2-0 molar HCL. And I'm going to use the titrate with the HCL.

With the borax. So I'm going to put a little bit of borax in there. Make sure that I rinse that.

And this all solutions can go down the same way. Okay. So I'm going to fill this one up here with the .

So I'm going to follow the same procedure. So remove the bubble. So we follow the same procedure. We are going to read the initial volume of the puree.

So right now it's at 1.40. Again, we're going to measure the volume to 0.01. Alright, so now I'm ready for titrate. I have HCl, I have borax.

Initial color is blue, so we want that yellow color. That's an acidic solution. So again you want that persistent yellow color.

As you can see I'm still adding, going a little fast at the beginning. So as you get closer to the endpoint, you see a yellow color where the acid touches the solution. So we still have the, so as you can see the solution is no longer white, white blue.

So that's the color that you want. So that means that that's the end point. Alright, so again you want to be careful that you can't close the envelope so that you don't overshoot the envelope.

Alright, so for the other reactions we have test tubes at different temperatures. So we have to do at 45 degrees, have the same titration at 45 degrees, and average the volume. You're going to find that the volumes of the acid used are two different temperatures.

Now, so you have to do this five times, twice at each temperature, so the role of 10 titrations. Okay? Your first data set should look like this. You have the volume of HCl that you use to titrate with the borax.

You have temperatures for each pair. For the five degrees, you have two volumes. Then you're going to calculate the moles of borax that was present in the saturated solution using this equation. So remember the equation for titration.

You have one mole of borax equivalent to two moles of borax. So you're going to use that equation to calculate the moles of borax. And then you're going to use equation 3 to calculate Ksp and then find ln of Ksp. So once you have the ln of Ksp, you're going to plot that against 1 over T.

That should give you a straight line with an intercept and a slope. So the slope will be negative delta H over R. The intercept will be delta S over R.

Slope will be negative delta H over R. You can calculate delta H and the Y intercept. is delta s over r then you're going to use that to calculate delta s you have to calculate the delta g so there are two ways two methods of finding finding delta g so you can use this equation here RT ln of ksp at each temperature or the second method you can use delta g equal to delta h minus T Delta S. So these values you calculate from the previous slide. So you have to do both of these methods for this experiment. Now when you have both Delta G at using the two methods, so you can upload Delta G as a temperature in one graph.

The critical parts of this experiment is temperature control and transferring the solution. Make sure that you are not transferring the solid. Some things to remember.

is if your solution temperature is changing rapidly and you get an accurate temperature reading so think about that if you pour a saturated solution at 45 degrees into a test tube which is called at 20 degrees Celsius what's going to happen? so that's something to think about something else to think about is once the saturation of the saturated solution is in a test tube it doesn't matter how much water you use to get it back out and heat it to alumite flask for titration don't forget to record temperature to nearest 0.1 degree Celsius, average temperatures before and after sampling, mix the solution as well to ensure that you get to equilibrium. So the water bar should not be more than 50 degrees Celsius so otherwise the borax will start decomposing.

Make sure that there are no air bubbles in the burette tip and write down the concentration of standardized HCL for the calculation. So just for your information, just because delta G is positive doesn't mean things won't dissociate or dissolve for example acetic acid is a weaker acid than HCl but it dissociates in water the dissociation is not favorable it doesn't dissociate more than HCl so the lab report is as usual okay so you have to show sample calculations data tables and observations be careful with sig fix so you're going to plot delta G temperature for two methods okay and then summarize your results conclusion the discussion part and then answer these questions good luck

Transcript for:Equilibrium and Thermodynamics Experiment

Transcript for:
Equilibrium and Thermodynamics Experiment