experiment 3 liquid diffusion apparatus
DESCRIPTION
EAT 347 Mass TransferSchool of Environmental EngineeringTRANSCRIPT
EXPERIMENT 3
LIQUID DIFFUSION APPARATUS
1. Objective
Understanding the calibration of different mol of CaCO3 to obtain Cm value.
Demonstration of liquid diffusion.
Determine the diffusion coefficient of CaCO3 solution in deionized water.
2. Introduction
Diffusion can be described as a mixing process on a microscopic scale, caused by the
molecular motion of the particles. In liquids it is a slow process, and this slowness is
responsible for its importance. It can be the rate determining step in many mass transfer
operations, such as distillation, extraction, and in industrial reactions using porous catalyst. It
controls, for instance, the release of flavour from food. Therefore, knowledge of diffusion
rates is important for the design of process equipment. The common models can describe
molecular diffusion in multicomponent liquids is a generalisation of Fick’s Law to
multicomponent system. Fick’s law is a phenomenological description of diffusion for binary
liquid systems. Molecular diffusion describes the relative motion of individual molecules in a
mixture induced by their thermal energy causing random, irregular movements. But it may
also arise from pressure gradients, temperature gradients, external force fields, and
concentration gradients. The resulting net diffusion flux is down the potential gradient, i.e. in
the case of a concentration gradient from regions of higher to lower concentration until
uniformity of the system is reached.
3. Equipment
LEGEND
A = J- Tube stand
B = J- Tube with honeycomb
C = Conductivity probe
D = Conductivity meter
E = Magnetic stirrer
F = Liquid vessel
4. Safety and precaution
Be careful when handling the glassware
Do not attempt to change the setting of the digital conductivity meter
Wear protection glove and eyewear when preparing the test solution
5. Procedure
5.1 Pre-procedure
1. Before conducting the experiment read the safety instruction.
2. Before lab sessions read and understand the theory for liquid diffusion.
3. The accessories need to be prepared for the experiment.
5.2 Experiment Procedure
Experiment A
1. The solution for 0.001, 0.0012, 0.0014, 0.0016, 0.0018 and 0.002 M of CaCO3 was
prepared.
2. The conductivity value for all the different M of CaCO3 was determine by using the
conductivity probe and meter (C,D).
3. The reading was recorded in the table provided.
4. The graph of concentration of Ca2CO3 versus conductivity (Siemens) was computed. The
slope of this line is the (CM).
5. By using deionized water clean and washed the probe to removed all traces of salt after
finished the experiment.
Experiment B
1. The solution of 0.1 M CaCO3 was prepared.
2. The number of capillaries (holes) of the PVC round plate in the J-tube (B) was
determined. (the diameter is 2mm while the height is 6.8mm)
3. The higher end of the J-tube was clamped to the J-tube clamper (A). During clamping the
J tube need to be careful.
4. CaCO3 solution was poured into the J-tube until the liquid just reached the tops of the
capillaries. The excess solution need to wipe kindly by using soft tissue.
5. The conductivity probe (C) was inserted to the liquid vessel (F). The cable are ensured
connected to the digital conductivity meter (D).
6. The digital meter was connected to laboratory 240V AC power supply. The power supply
was switched on.
7. The liquid vessel was placed on the magnetic stirrer (E). The white magnetic bar was
placed into the liquid vessel.
8. 1000ml of deionized water was poured into the test vessel (F).
9. The magnetic stirrer was switched ON. Regulated the stirring speed to about 200 rpm.
10. The conductivity meter was switched ON. Reading shown in the meter was ensured.
11. The J-tube was placed into test vessel. During this procedure make sure that is careful. No
solution should be dropped to the deionized water.
12. The test vessel was filled with small amount of deionized water until the capillary tops
are submerged approximately 5mm below the surface of the water.
13. Start the stop watch when the capillary tops was submerged.
14. Kindly take the conductivity value for every 5 minutes elapsed until 30 minutes.
15. Removed all the glassware and rinse with deionized water after the experiment is done.
16. Disposed the test liquid in the laboratory sink.
6. Results
Experiment A
Concentration (Mol/L) Mass (g) Conductivity (µS)
0.001 0.05 204
0.0012 0.06 201
0.0014 0.07 206
0.0016 0.08 202
0.0018 0.09 205
0.002 0.10 203
CaCO3 = 100.23 g, Volume of solution: 500ml = 0.5 L
Calculation for Determining the Mass of CaCO3
To prepare 0.001 M, 0.0012 M, 0.0014 M, 0.0016 M,0.0018 M, 0.002 M solution;
100 g/ mol x 0.001 mol/L = 0.1 g/L x 0.5 L = 0.05 g
100 g/ mol x 0.0012 mol/L = 0.12 g/L x 0.5 L = 0.06 g
100 g/ mol x 0.0014mol/L = 0.14 g/L x 0.5 L = 0.07 g
100 g/ mol x 0.0016 mol/L = 0.16 g/L x 0.5 L = 0.08 g
100 g/ mol x 0.0018 mol/L = 0.18 g/L x 0.5 L = 0.09 g
100 g/ mol x 0.002 mol/L = 0.2 g/L x 0.5 L = 0.1 g
Experiment B
Concentration = 0.1 M, Volume of solution: 50 mL = 0.05 L
Calculation for Determining the Mass of CaCO3
100 g/ mol x 0.001 mol/L = 0.1 g/L x 0.05 L = 0.005 g
Time (Minute) Conductivity (µS)
0 190
5 190
10 190
15 191
20 191
25 192
30 192
Graph for experiment A :
Graph for experiment B :
For experiment B, the diffusion of CaCO3 can be determined using the following equation;
D = (4∙V∙X / M∙N∙ d2Π∙CM) x (Dk/Dt)
Where
D = diffusion
V = volume of water container for the J tube (1000mL)
X = height of J tube
M = moles of CaCO3
N = number of capillary on J tube
d = diameter of J tube
CM = slope value from experiment 1
(Dk/Dt) = slope value from experiment 2
7. Discussion
From experiment A, it can be observed that the values given off by the conductivity meter
fluctuates to inconsistent values. The value changes so well that it is as though as the
concentration is increased (0.001M, 0.0012 M so forth) they have no direct relation with the
conductivity displayed. This is due to the amount of moles of calcium carbonate in the
solution that is too low, not every particle within the solution participates actively in the
reaction with water.
Experiment B is somewhat similar to experiment A. As time lapses, the conductivity
meter increases but lands flat under certain interval. For instance, during the first 10 minutes,
the value remains at 190 µS before it rises to 191µS 5 minutes later. The experiment ends
after it is conducted for 30 minutes and the final value reads 192 µS. Difference with
experiment A is that the value gradually increases with time, instead of fluctuating
inappropriately when more concentrated mixture is introduced to the conductivity meter.
Reason why this phenomenon occurs is because the solution used is only at 0.1 M of calcium
carbonate, therefore large difference of value cannot be expected.
8. Question
8.1 Give three (3) example of liquid phase diffusion phenomenon in the environment.
Diffusion phenomenon of sugar molecules from high concentration to low one.
Diffusion phenomenon when one drop of ink is spreading in a cool and hot water.
Diffusion phenomenon when I2 molecules are spreading in alcohol.
8.2 Describe why conductivity can be use as a parameter to measure the rate of mass
transfer in this experiment.
The parameters to describe the retention properties of the liquid and the capillary
movement of the liquid were determined by using experiment. The conductivity can
use to measure the rate of mass transfer because the readings are accurate and this is
one the equipment that suitable to use in laboratory and easier to handle.
9. Conclusion
The objective of the experiment is to understand the calibration of different mol of CaCO3 to
obtain Cm value. Besides that, it is aimed to demonstrate the diffusion of liquid. It is also
conducted to determine the diffusion coefficient of CaCO3 solution in deionized water.
Based from the experiment, it is found that diffusion, a mixing process on a
microscopic scale, caused by the molecular motion of the particles, of calcium carbonate in
water can be observed and determined by it’s conductivity. This is done by conducting the
experiment based on the instructions found in this written report. On that basis as well, safety
aspects was not neglected. Glassware was handled with care, the setting of the conductivity
meter was not readjusted and necessary protective gear was worn when preparing the test
solution.
Knowledge of diffusion rates is important for the design of process equipment.
Therefore this is the reason why the experiment was conducted, so to provide students with
necessary exposure, especially with a simple experiment as such.
10. Reference
http://iopscience.iop.org/0508-3443/6/4/306/.../0508-3443_6_4_306.pdf
www.legionbrothers.com/products_heat.html
www.mechanicalduniya.com/.../practical-list-for-heat-and-mass.html