CHEM10003 Experiment 2: The Preparation of Paracetamol
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Chemistry1 CHEM10003
Experiment 2: The Preparation of Paracetamol
2022
Experiment 4: Vapour Pressure of a Volatile Liquid
Name:
Day/Time/Group number: (class you attended)
Aims:
• To observe the changes in equilibrium vapour pressure of a volatile liquid with temperature, from vacuum line measurements
• To determine a value of the latent heat of vapourisation of a liquid.
Experimental:
Refer to Student Notes Experiment 4 University of Melbourne 2022
Results:(Tables of data)
PART A: MANOMETER PRESSURE MEASUREMENT
Manometer pressure reading, prior to start of experiment: 1 m bar______________
PART B: TABLE 1 VAPOUR PRESSURE MEASUREMENTS
Liquid Sample: Name n-pentane Formula C5H12
TEMP (oC) |
TIME (min) |
MANOMETER READING ( Pm mbar) |
|
TEMP (oC) |
TIME (min) |
MANOMETER READING ( Pm mbar) |
4.6 |
0 |
286 |
5.2 |
0 |
336 |
|
4.4 |
1 |
284 |
5.0 |
1 |
318 |
|
3.0 |
2 |
273 |
4.9 |
2 |
318 |
|
2.5 |
3 |
269 |
5.0 |
3 |
317 |
|
2.0 |
4 |
266 |
5.0 |
4 |
317 |
|
2.0 |
5 |
265 |
5.0 |
5 |
317 |
|
2.0 |
6 |
265 |
|
|
|
|
Equilibrium Vapour Pressure: p = 265 at 2.0 ºC |
Equilibrium Vapour Pressure: p = 317 at 5.0 ºC |
Manometer pressure reading, after experiment: 1 m bar______________
Part C: TREATMENT OF DATA
TABLE 2: Equilibrium vapour pressures of n-pentane at different temperatures.
Experimental data sets measured at different T (°C): Data for graph:
TEMP(°C) |
TEMP (K) |
EQUILIBRIUM VAPOUR PRESSURE (mbar) |
|
ln p |
use scientific notation |
275.15 |
265 |
|
|
0.00363 |
|
5 |
279.15 |
317 |
|
|
0.00353 |
10 |
284.15 |
382 |
|
|
0.00351 |
15 |
289.15 |
461 |
|
|
0.00346 |
20 |
294.15 |
563 |
|
|
0.00340 |
Graphing data – use Excel or plot by hand and paste below
Plot ln p (y-axis) versus 1/T (x-axis).
If using Excel
Equation of the line:_________________________________________________________
R 2 value:__________________________________________________________________
Excel Graph: Use this data in Q2, Q3 and Q4 below
Questions:
REMEMBER THAT ANSWERS NEED TO BE SUPPORTED BY EVIDENCE FROM YOUR DATA OR THEORY
Question 1
Consider the diagram of the vacuum line below; the line is under vacuum and the manometer has a pressure reading of 1 mbar. The system has developed a leak at one of the connections. What do you expect to happen to the pressure reading over the next ten minutes and why?
If the system has developed a leak at one of the connections. Propane will begin to melt into liquid. Because the leak will continuously enter the air into the pump. The pressure will begin to rise until the pressure in the pump and the atmospheric pressure balance. As the pressure in the pump rises, the liquid nitrogen begins to boil. So propane will begin to melt into a liquid.
Question2
Using the equation of the regression line from your Excel plot, what is the gradient of the line of best fit (show units)? Or if hand plotted, show working and determine gradient of the line:
Question 3
Calculate the heat of vapourisation (ΔHvap) of n-pentane from the gradient of your graph according to equation 4.2 (include units). Show all working.
Question 4
Using the value of ΔHvap obtained from your graph and a pressure-temperature data pair (lnp1 , 1/T1) from the graph, calculate the normal boiling point of n-pentane using equation 4.3. Show all working.
[HINT: The normal boiling point (T2) will be at the atmospheric pressure, ρ2 = 1013 mbar. The universal gas constant R is 8.314 JK−1mol−1].
Data pair from line of best fit: lnρ1 value_______________ 1/T1 value_________________
Question 5
Complete Table 3 below, comparing the properties of water and pentane, adding your values determined from the experiment and the Prelab. Question regarding safety advice for use of pentane (with bibliographic reference):
Table 3 Comparison of properties of water and pentane
Properties/Substance |
H2O |
C5H12 pentane |
Molar Mass (g/mol) |
18.01 |
|
Density of liquid (g/mL) |
1.00 |
0.63 |
Normal b.pt. (oC) |
100 |
|
DHvap (kJ/mol) |
40.7 (at 100oC) |
|
Flash Point (min. temperature at which vapours will ignite) (oC) |
Not applicable |
- 49.0 |
Safety |
nontoxic |
(List all properties found)
|
Reference for safety data:
…………………………………………………………………………………………………………………………………………..
In the polymer industry, pentane is added to preformed granules of polymer. The mixture is heated to the boiling point of pentane, which vapourises and expands in volume leaving tiny voids/empty pockets in the structure of the polymer (pentane is called a ‘blowing agent’). This makes a light, low density product.
In the production of the polymer, pentane or water could be used as a blowing agent.
Identify one advantage and one disadvantage in using pentane rather than water with a brief explanation.
(Are there any environmental/energy/safety concerns, based on the data in Table 3?
Note: There are environmental concerns associated with waste and decomposition of polymers but this question refers to the manufacture of polymers.)
Advantage:
Disadvantage:
Conclusion:
(What have you found out?)
2022-08-25