This is a Lab Procedure and Data for The Thermodynamics of Potassium Nitrate Dis

Question

This is a Lab Procedure and Data for The Thermodynamics of Potassium Nitrate Dissolving in Water lab. And I need help with the calculations and graphs. Materials e Potassium nitrate (KNOl Centigram balance 600 mL Beaker 100 mL Pyrex graduated cylinder · . . . . e 3-prong clamps (1 medium, 1 small) Hotplate Scoopula Weigh boat Collection jar (KNO, will be collected) Jack . Ring stand Thermometer (20-110c) .Wire loop with straight end Procedure X Place a hot plate on top of a raised jack on top of a ring stand, and then place a 600-mL beaker half filled with tap water on top of it al Using a centigram balance, weigh approximately 20 g KNO3 in a weigh boat. Record the exact mass in your lab notebook. Quantitatively transfer the KNO, into a 100.0 mL Pyrex graduated cylinder. Rinse the weigh boat only if necessary with a small amount of water and add the washings to the graduated cylinder. Add 10.0 mL of distilled water to the graduated cylinder. Remove the plastic base from the graduated cylinder and submerge the graduated cylinder into the water bath such that the base of the graduated cylinder is approximately 1 cm away from the bottom of the beaker. Secure the graduated cylinder using a clamp. Insert a thermometer into a rubber adapter. Use mineral oil to lubricate the thermometer if necessary. Place a spiral wire loop round a thermometer and place the thermometer inside the graduated cylinder so the bulb is well below the surface of the liquid, but not touching the bottom of the cylinder. Clamp the rubber adapter to secure the thermometer to the ring stand Heat the solution, while stirring, until all the solid KNO, dissolves. Remove the graduated cylinder with KNO, solution from the hot water bath by lowering the jack apparatus/hot plate/600 mL beaker. 4. 5. 6. 7. 8. 9. 10. Allow the solution to cool while constantly stirring. Record the temperature and the volume (without the wire loop and thermometer) of the solution when the first crystals reappear. This corresponds to the temperature at which the solid KNO, is assumed to be in equilibrium with the solution 11. Add 5 ml of distilled water to the graduated cylinder containing the KNO, solution. 12. Raise the jack apparatus once again and repeat the heating and cooling process. 13. Continue adding 5 mL water and repeating for a total of seven determinations. U.01

Explanation / Answer

Your data is really disordered. Let me guide you of how you'll do calculations and then the graph.

To get the number of moles of KNO3, use the molecular weight ot KNO3 (which is 101.3 g/mol). I think I read the mass is 20 g right? then the moles:
moles = 20/101.3 = 0.197 moles

To get the concentrations, just divide these moles between the volume there (volume in L not in mL, just divide between 1000 the volume) for example:
C1 = 0.197 / 0.02361 = 8.34 M

This is the concentration of KNO3, (which will be the same as K and NO3 ion)

To get Ksp = [K][NO3] so:
Ksp = 8.34*8.34 = 69.56

To calculate Temperature in kelvin, just sum 273 to the temperature in C:
K = 273 + 16 = 289 K

To get 1/T: 1/289 = 3.46x10-3 K-1

To get lnKsp: ln69.56 = 4.24

To get dG: dG = -RTlnK
dG = -8.3144 * 289 * 4.24 = -10188.13 J/mol

once you got all the values, plot lnKsp vs 1/T to get from the slope the value of dH and the y intercept the value of dS. This is because, what you are really plotting is this:
lnKsp = dS/R - dH/R(1/T)

So the y intercept will give you one value, then, equal that to dS/R and solve for dS: dS = y-inter * R
The slope is dH/R, so: dH = R * slope

Use R = 8.3144 J/mol K

That's how you'll do it.

Hope this helps

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