Lab 10 Thermodynamics of Dissolving Urea PDF

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Lab report over Lab 10 Thermodynamics of Dissolving Urea...

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Lab 10: Thermodynamics of Dissolving Urea

Dustin Smith [email protected] CHEM 1440.330 1 April 2019 Monday 3:00PM- 6:00 PM Fredy Medina

Summary: The goal of this experiment is to is to determine the Keq, or the equilibrium constant, and ΔH, or the change in enthalpy, for the dissolution of urea in water. Using this information we will calculate the total energy available, ΔG, and the change in entropy, ΔS. Urea, CO(NH2)2 , is an organic compound produced in the body. The liver converts Ammonia, NH3 , into urea so that the kidneys can remove it via micturition, or urination. In order to see how well your kidneys are processing urea, doctors may run a Blood Urea Nitrogen (BUN) test. Procedure: Part 1: Calibrating  the temperature probe for the lab Step 1. Open up the capstone program. Make sure that you have turned on your temperature probe and have connected it to the program Step 2. In a 250ml beaker you will fill the beaker to about 230 ml with ice and then about 10 ml of water. In another 250 ml beaker you will fill about 240 ml of room temperature water. Step 3. Place the temperature probe into the ice and water mix and allow the probe to stabilize to the temperature of the solution. Step 4. After stabilizing the first point of the calibration process, remove the probe from the ice solution and submerge the probe in the room temperature water. Allow the probe to stabilize again to the new bath. Part 2: The Experiment Step 1. Measure out 3.003g of urea and place it into a 100 ml graduated cylinder. Step 2. Then proceed to pour in DI water until you reach 50 ml. Step 3. Stir the urea/water solution until the urea completely dissolves into the water. Doing this will show that the urea will completely dissolve in the calorimeter. Step 4. Measure out another 3.003g of urea, and this time place it into the calorimeter. Step 5. Pour another 50 ml of water into the calorimeter.  fter you add the water, insert the temperature Step 6. IMMEDIATELY a probe into the calorimeter and start recording the temperature of the solution until the temperature stabilizes.

Observations and Results:

We calculated our Keq  was 1.00. Using the Keq  formula we found Keq  by taking the  molar mass of Urea (60.06g/mol) and dividing it by the volume of the entire solution (.05L). In the calorimeter we started out with 22.5°C and ended with 19.5°C

In order to calculate ∆H we used the ∆H formula. m=mass of reactants (50.545g), c=specific heat (4.186 J/g°C), and ∆T= change in temperature (-3°C). In order to find ∆G we used the ∆G formula. R=gas constant (8.3145 J/mol·K), T=292.6K, ln (natural log) of Keq, Keq =1.00 To calculate ∆S we used the ∆S formula where ∆G=-3.24kJ/mol, ∆H=12.671kJ/mol, and T=292.15K Formulas Used: Keq= Molar mass of urea/ total volume of Litres of solution ∆H=(-m·c·∆T) / moles of urea ∆G=-R T lnKeq ∆S=(∆G-∆H)/ -T Other Pictures:

In Conclusion: This experiment allowed us to find Keq, ∆H, ∆G, and ∆S. In order to do so we first needed to dissolve 3.003g of urea in 50 ml of water to determine the equilibrium constant, or Keq. We then repeated this experiment in a calorimeter in order to find the temperature change. Using this new data we were able to find the rest of the measurements. Our experimental ∆H and ∆S values were lower than the corresponding literature values, while our ∆G experimental value ended up higher than the corresponding literature value. Any inconsistencies between the values is either result of incorrect calibration of the temperature probe or incorrect values in our formulas....