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Maria Faye Stephanie Cantago                                                                      January
29, 2018

Zaham Zaragoza

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Exercise 1






A.    Diffusion
of gas in a Gas

According to
Graham (1829), equal volumes of different gases diffuse in very unequal times
which also has an inverse relation to the specific gravity of the gas and its
density. Furthermore, the vapor or gas will be propagated to any distance, by
exchanging positions with a train of particles of air, according to the law of diffusion.
The length, to which this diffusion proceeds, in a confined portion of air, is
limited by a property of vapor, namely, that the particles of any vapor
condense when they approximate within a certain distance (Wisniak, 2013).




1 m

18.3 secs

0.054 m/sec

2 m

min 39 secs


3 m

2 mins 5 secs

0.024 m/sec

4 m

3 mins 38 secs

0.018 m/sec


4 mins 56 secs

0.017 m/sec

Table 1. Rate of diffusion of
perfume in a close room.

            The material used in the experiment
is a perfume placed in a petri dish and was left to evaporate and diffuse in a
close room. The different distances covered by the experimenters were one to
five meters. The result was obtained by how long will the gas take to diffuse
in the air and reach the experimenters olfactory system.

When the perfume
evaporated and diffused, there was no outside air to help it spread faster
across the room. The farther the student was from the perfume, that longer the
time it took for the student to smell the perfume (Table 1). As the molecules
of the perfume slowly travel across the room, it moves randomly, bumping the
air molecules in the room and made the travel of the gas to the experiments
olfactory system to be longer.


B.    Diffusion
of a Solid in a Colloidal Solution

The diffusion of
solids has the slowest rate, however, this depends on the interaction of the
solid to its medium (“Why does diffusion take place”, 2016). The diffusion rate
of solid is also affected by the weight of the solid. As the molecular weight
increases, rate of diffusion decreases. Another thing that can affect the rate
of diffusion is the temperature (“Why does diffusion take place”, 2016). As the
temperature increases, the rate of diffusion also increases.

Figure 1. Graph of the diffusion rate of
solids in a colloidal solution.










Table 2. Diffusion
rate of different solids in a colloidal solution.


of Diffusion

Potassium permanganate (158g/mol)

0.402 mm/ min

Methylene blue (327g/mol)

0.016 mm/ min

Potassium dichromate (294g/mol)

0.225 mm/ min


In the
experiment, potassium permanganate, with a molecular weight of 158 g/mole, has
the highest average rate of diffusion. This is followed by potassium
dichromate, having a molecular weight off 294 g/mole, and methylene blue, with
374 g/mole molecular weight. The trend indicates that the lower the molecular
weight of a substance, the faster it diffuses in the agar (Table 2 and Fig. 1).
Thus, confirming that the rate of diffusion of a substance is affected by its
molecular weight.

C.   Diffusion
of a Solid in a Liquid

        The diffusion of solid in the liquid
medium involves a separation of solute from the surface of the solid and the
disintegration of the solute molecules into the liquid phase (Hsu and Liu,
1993). The diffusion rate of solid in liquid is relatively faster compared to
the diffusion of solid in a colloidal surface. Other factors that may affect
the diffusion rate of solid are temperature, mass and size of the particle.


Figure 2.
Potassium permanganate crystal slowly diffusing in the container


        In the experiment, potassium
permanganate was used as the solid that diffused in the liquid medium which is
water. The potassium permanganate crystal slowly dissolved in the bottom of the
beaker and starts to diffuse. This process is called dissolution which is due
to the diffusion of the solid particles. After 30 minutes, the potassium
permanganate, the purple dye (Fig. 2), finally covered the bottom part of the
beaker. Furthermore, the size of the potassium permanganate crystals also
affected the rate of the diffusion since the larger the surface area, the
faster the diffusion rate (“Study of Diffusion of Solids in Liquids”, 2015).


         Osmosis is a passive transport of
water molecules across a semi-permeable membrane following the concentration
gradient of the solute. Therefore, osmosis can only occur under specific
conditions where a) two aqueous solutions are separated by a membrane that is
permeable to water but impermeable to at least one of the solutes in the
solution and b) there is a difference in the total concentration of impermeable
solutes between the two solutions (Finkler, n.d.).

Table 3. Weight of the diffusing membranes with NaCl and
distilled water every 5 minutes.


filled membrane in water solution

filled membrane in NaCl solution

0 mins

136.12 g

141.03 g

After 5 mins

142.25 g

137.97 g

After 10 mins

142.82 g

138.28 g

After 15 mins

142.61 g

137.84 g

After 20 mins

143.36 g

138.38 g

After 25 mins

143.49 g

138.17 g


      In the experiment, pig intestines were
used as dialyzing membrane to imitate the function of the plasma membrane. The
NaCl filled dialyzing membrane absorbed water from the water solution at the
start of the experiment while the water filled dialyzing membrane lost its
water to the NaCl solution. However, as the osmosis continues for 30 minutes,
the rate of the two set-ups decreased as the solution outside and inside the
dialyzing membranes slowly reaches equilibrium. A notable inconstant decrease of
the weight was observed in the water filled membrane which may be caused by the
attempt of the membrane to reach equilibrium.

Hemolysis and Crenation

The net movement
of water into and out of the cell is driven by the difference in osmotic
pressure between the extracellular and intracellular fluids (Finkler, n.d.).







Figure 3. Illustration of red
blood cells when exposed to (A) distilled water, (B) 0.9% NaCl and (C) 3% NaCl.



Under the
microscope, the red blood cells from the solution with distilled water swelled
and burst.  In the solution with 0.9%
NaCl, there was no apparent change to the red blood cells. The red blood cells
of the solution containing 3.0% NaCl shriveled.





Literature cited:

Graham T., (1829). A Short Account of Experimental Researches on
the Diffusion of Gases Through Each Other, and their Separation by Mechanical
Means. Quart. J. Sci., 2, pp. 74-83

Hsu, J. and Liu, B. (1993). Dissolution
of solid particles in liquids: A reaction—diffusion model. Colloids and
Surfaces, 69(4), pp.229-238.

Linge (1981),
Adv. Colloid. Interface Sci.. 14. pp 239.

Finkler, M.
(n.d.) Osmosis, Tonicity, and Concentration. Indiana
University Kokomo
Science, Mathematics, and Informatics Department

Study of
Diffusion of Solids in Liquids | Chemistry Science Fair Project. (2015).

Why does
diffusion take place. (2016). A plus topper.

J. (2013). Thomas Graham. II. Contributions to diffusion of gases and liquids,
colloids, dialysis, and osmosis. Educación Química, 24, pp.506-515.



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