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Experiment 5A JKP
Transcript of Experiment 5A JKP
Hydrophobic colloids are water hating.
Hydrophilic colloids are water loving. Experiment # 5A: Colloids Jessica Ann B. Jorge
Bea Shane Monasterio
March 9, 2013 Introduction Objectives & Scope Theoretical Framework To be able to differentiate the condensation method from the dispersion method in preparation of colloids To identify the classifications of colloids To observe the different properties of colloids Methodology Preparation of Colloids Tyndall Effect Preparation of Patriotic Tube Precipitation Discussion Sulfur Sol Fe(OH)3 Sol Emulsion Patriotic Tube Precipitation Tyndall Effect Errors: explained Conclusion Guide Questions Question 1
Why is Sulfur not soluble in water? What kind of colloidal dispersion is a sol? Answer: Question 2
How would you account for the procedure in IA-b2? Answer: Question 3
What is the role of shampoo solution in the oil emulsion prepared in procedure IB? Question 4
Give an explanation for the results obtained in procedure II. What ions/ compounds are responsible for the different colors observed in the Alexander’s patriotic tube? References Answer : Answer: Answer: Question 5
What causes Tyndall effect? When soap is mixed with an oil- water solution, the soap molecules work as a bridge between polar water molecules and non-polar oil molecules. Since soap molecules have both properties of non-polar and polar molecules the soap can act as an emulsifier. An emulsifier is capable of dispersing one liquid into another immiscible liquid. FeCl3 forms a lyophobic colloid. Hence in this case, the Fe(OH)3 sol needed a special process in other to be mixed which is through the process of hydrolysis.
FeCl3 + 3H2O Fe(OH)3 + 3HCl Colloidal solution of certain substances such as sulfur which are soluble in alcohol but insoluble in water can be prepared by pouring their alcoholic solution in excess of water. When the mixture of hot alcohol and sulfur was added in water, the alcohol dissolved in water, turning the medium cloudy. Tyndall effect which was first explained by the British physicist John Tyndall. He observed that when a beam of light is allowed to pass through a colloidal solution, the path of light gets illuminated. It occurs because light is scattered by particles present in colloidal solution. Sulfur is a nonpolar substance and water is polar. Hence according to the "like dissolves like" rule, polar water will not be able to dissolve Sulfur. The shampoo solution acted as the emulsifier that "bonded" the water (polar) and the oil (nonpolar). When nonpolar Sulfur was dissolved in ethyl alcohol, it dissolved in the nonpolar end of the alcohol. The said solution was then mixed with water to form the sol. The Tyndall effect is the scattering of light due to the presence of colloidal particles which are able to maintain a homogeneous appearance yet are large enough to be able to scatter light. Since the dimensions of colloidal particles are comparable to the wavelength of ultraviolet and visible radiations, they scatter radiations and get illuminated thus exhibiting the tyndall cone. n.a. (n.d.). Properties of Colloids, Effects of Colloids, Properties and Tyndall Effect, Brownian Movement, Coagulation. Sakshi Education . Retrieved on March 3, 2013. From http://www.sakshieducation.com/(S(bt43kq45r5myxi555goypeia))/Inter(new)/InterPDFStory.aspx?nid=15827&cid=22&sid=174&chid=169&tid=96.
n.a. (n.d.). Colloids. Infoplease . Retrieved on March 3, 2013. From http://www.infoplease.com/encyclopedia/science/colloid-colloids-solutions-mixtures.html.
n.a. (October 5, 2011). Tyndall Effect.Tutapoint . Retrieved on March 5, 2013. From http://www.tutapoint.com/knowledge-center/view/82.
n.a. (n.d.). Colloids & Suspensions. Chemistry Principles. Retrieved on March 5, 2013. From http://www.wavesignal.com/Principles/7.Solutions/Coll.html.
n.a. (n.d.). The Colloidal Solution. Retrieved on March 3, 2013. From http://download.nos.org/313courseE/L-7%20THE%20COLLOIDAL%20SOLUTION.pdf. S. Ramakrishna.(n.d). Precipitation of Colloids. Textbook of Medical Biochemistry. Retrieved on March 7, 2013. From http://books.google.com.ph/books?id=BVpD
a. aq. layer
FeCl3 + 3H2O--> Fe(OH)3 + 3HCl
b. dark blue layer
4 FeCl3 + 3 K4[Fe(CN)6]--> 12 KCl + Fe4[Fe(CN)6]3
c. Acidic layer (HCl)
d. pink gel
- Phenol red acts as PH indicator and it is pink due to NaOH which is basic
The ordering of each layer is due to the density of the ions/compounds present in each layer. Rationale and Significance The purpose of this experiment is to understand the very concept of what a colloid is and how is it essential in our everyday living.
It aims to give the students a better grasp of the difference between a colloid and other mixtures through identifying its specific characteristics and properties.
Thus, they will be able to apply what they have learned in order for them to gather more ideas on the said topic and its possible applications to other fields, especially in future technological advancements. Gel (liquid in a solid) Other Properties: Aerosols (solid/liquid in a gas) Foam (gas in a liquid) Emulsion (liquid in a liquid) Sol (solid in a liquid) Can be classified into: May be: Electrophoresis (motion of dispersed particles under the influence of a uniform electric field) Brownian Motion (random movement of particles) Has 2 phases: Lyophobic (solvent-hating) Lyophilic (solvent-loving) Tyndall Effect (bending of light) Continuous/ Dispersing phase (medium) Dispersed phase (particles suspended) Colloids The Alexander’s Patriotic Tube that was prepared formed four different layers of different colours.
The pink agar layer was formed from the reaction of phenol red with presence of NaOH.
The blue layer was formed by the formation of Iron Ferrocyanide.
After FeCl3 was added, a white layer was produced when an acidic layer of HCl was formed from the reaction of water and excess FeCl3
4 FeCl3 + 3K4[Fe(CN)6] ---> 12KCl + Fe4[Fe(CN)6]3.
The topmost yellow layer was formed as a prodcut of the reaction of H2O and FeCl3. Limitation of experiment
impurities in the substances
reactions Colloids exhibits certain characteristics of both a suspension mixture and a solution. However, individual properties such as the possibility of a Tyndall effect, which was defines as the scattering of light due to the presence of suspended colloidal particles, has provided the ability to distinguish colloids from other mixtures. There are two ways to prepare a colloidal system : Dispersion happens when a larger particle is reduced to a smaller one.
Condensation occurs when a dispersed phase is condensed to a bigger particle. One method of separating colloidal particles is by coagulation, where the colloidal particles are enlarged.
The FeCl3 sol colloid was separated through three different precipitants. Due to the number of moles of Na and the anions from each precipitant, the amount of precipitate was affected. Table 1: Systems and Observations
Tyndall Effect (presence / absence x) Figure 1.1: Fe(OH)3 Sol Figure 1.2: Sulfur Sol Figure 1.3: Emulsion Figure 2: Patriotic tube Figure 3: Tydall Effect Figure 4: Precipitation Results Table 2: Precipitation Observation Table 3: Classifications of Colloids Figure 1.2: Sulfur Sol Figure 6: molecule Figure 7: Polarity Figure 3: Tyndall Effect Different types of colloids could be classified according to the states of the dispersing phase and medium involved. They could also be classified into hydrophobic or hydrophilic colloids.
Hydrophobic colloids are water hating
Hydrophilic colloids are water loving