I just need the calculation part done.
The mass of the solutes is as follows:
.502g Tris and .4999g KNO3 and .4995g Pb(NO3)2
Solution Calorimetry: Heat of Ionic Reaction
Solution Calorimetry is a convenient way of experimentally determining the heat of reaction in a liquid medium. Measurements in this lab will be made near room temperature and at ambient pressure. At the beginning of each measurement, a liquid is held in a Dewar flask while the other reactant is held in a glass cell immersed in the liquid. The glass cell is rotating to help stir the solution and keep it well mixed and homogeneous. Once both the liquid and the contents of the glass cell reach thermal equilibrium with each other, the bottom is pushed off of the glass cell and the contents of the glass cell are mixed and react with the liquid. In general, the reaction produces a heat change which causes the temperature of the reaction mixture, the glass cell and the inside of the Dewar flask to change temperature. During the measurement, the temperature is monitored with a sensitive thermistor and periodic temperature readings are written down. The temperature is plotted as a function of time from before the reactant is mixed with the liquid until the well after the reaction is complete. This temperature plot is called a thermogram and it can be used to calculate the heat of reaction.
This lab experiment requires good experimental technique to achieve accurate results.
The measurement apparatus is based on a Parr Solution Calorimeter. The calorimeter has an electric motor on the back which rotates the glass cell in the liquid held in the Dewar. It also contains electric circuitry to convert the signal from a thermistor immersed in the solution in the Dewar into a voltage which will re measured by a voltmeter. The voltage changes 100 mV for every 1¢XC change in temperature. However, to determine the heat of reaction, you need heat not temperature. The conversion factor between those two quantities is the heat capacity of the system. The system is almost a closed system consisting of the Dewar, the solution, the glass cell, lid and contents and the thermistor. The only major source of heat, other than the reaction, is the mechanical work done stirring the solution as the glass cell rotates. This is observed as a small increase in temperature with time; it will be removed from the data during the analysis of the thermogram.
Refer to the thermograms in Figures 1-2. The stirring of the calorimeter solution make the temperature rise slowly but uniformly with time ("drift line"), with a slope (dTemp/dtime) m1. Right after the reactant is added to the solution,, the temperature will start changing more rapidly for some time until finally the temperature will settle into a slow drift with a final slope m2. If things are simple, the two slopes will be the same, m1-m2, as in Figure 1. It is then very easy to see the initial point, I, where the reaction was started and the final point, F, where the temperature change settled back to the drift rate m2. Note that it is possible for the solution to cool during reaction. The corrected temperature change for the reaction is the difference in temperature at those two points minus the temperature drift during that time interval:
?´TC = TF - TI -m1(tF-tI)
For the thermogram in Figure 1, the data give:
?´TC = 273.89 K - 269.00 K -0.05 K/min (25 min-10 min) = 4.14 K
If the slopes m1¡Úm2, as in Figure 2, things are slightly more complicated. Points I and F are still selected as before, but now a third point D is also chosen. Point D is selected so that the area of G1 (the rough triangle with vertices I, A and D) is equal to the area of G2 (the rough triangle with vertices D, B and F). Then,
?´TC = TF - TI -m1(tD-tI) - m2(tF-tD)
For the thermogram in Figure D, the data give:
?´TC = 273.89 K - 269.00 K -0.05 K/min (17 -10) min -0.10 K/min(25 -10) min = 3.74 K
After the net corrected temperature change,?n?´TC, has been found, the energy or heat change is calculated as:
q = C ?´TC
where q is the heat of the reaction and C is the heat capacity of the calorimeter and sample. The C is determined during the calibration of the calorimeter. Once the heat of the reaction is determined, the enthalpy of the reaction is determined as:
?´HT = -q/m
Where m is the mass or number of moles of the reactant as appropriate and T is the average measurement temperature, roughly the point D.
In order to calculate the heat of the reaction, it is necessary to determine the effective heat capacity of the apparatus, including the liquid, the Dewar, the glass cell, etc. The effective C can be determined using a reaction where the ?´HT is well-known. One convenient reaction is the dissolution of the buffer TRIS (1,1,1-tris-(hydroxyl-methyl)aminomethane) in dilute HCl. The TRIS will neutralize some of the acid release large amounts of heat: q = m (245.760 J/g + 1.4364 J/g/K (25¢XC-T)) where T is the average temperature of the reaction and m is the mass of TRIS.
The TA will show you how to operate the Parr solution calorimeter.
For calibration of the calorimeter, add exactly 100 g of 0.100 M HCl to the dewar flask. Weigh 0.50 g TRIS into the Teflon sample dish or cell lid of the glass cell but record its weight as accurately as possible because it will directly affect the accuracy of your calibration. Assemble the rotating cell ensuring that it will not leak before you release its contents. Place the cell into the calorimeter and start the rotation of the cell. Set the thermistor controls so that the temperature can be measured with the voltmeter. Let the calorimeter equilibrate for 10-15 min. to allow the temperature in the reaction area to become uniform. Take this as your time zero and start recording the temperature every minute for 5 minutes. You can use the stopwatch on your cell phone to measure time. Use the rod to push the cap off the glass cell and let the reaction start. Record the temperature every 0.5 minutes for the next 15 minutes, for a total of 20 minutes of data.
After the measurement is over, stop the calorimeter motor, raise the cover and wipe any liquid off of parts not in the water. Remove the thermistor probe from the cover, and remove the sample dish or cell lid from the end of the push rod. Remove the push rod and release the glass cell from the drive shaft. Lift the Dewar flask out of the calorimeter and empty it in the waste container in the hood. Then wash and carefully dry all parts that came in contact with the solution.
Repeat the procedure to measure the heat of solution of solid potassium nitrate, KNO3, and solid lead nitrate, Pb(NO3)2, in distilled water. Use 100g of distilled water for the liquid in the Dewar and 0.50 g of each compound and repeat the temperature equilibration and measurement protocol used for TRIS.
Analyze the results from the TRIS to obtain the effective heat capacity of the calorimeter, that is, to calibrate it. Then calculate the heat of solution from your measurements on potassium nitrate and lead nitrate. Compare your measured ?´HT of solution with values you calculate from the Born-Haber cycle and data in your textbook or similar thermodynamic tables. Show your Born-Haber calculations.
I have attached two files. The document file explains how to do the ...
This solution explains how to use experimental data from a calorimeter to calculate enthalpy of solution. First, a standard compound is used to calibrate the calorimeter. After calibration, temperature changes are used to calculate the enthalpy of two experimental solutions.