esson 4 Lab: Chromatography and Ionic versus Covalent Bonds
PART 1
Begin by viewing the following Thinkwell video
27.1.2 CIA Demonstration: Chromatography
After you watch the above video, answer the questions below in sufficient detail:
(a) (3 pts.) This video discusses 3 different types of chromatography. List each one mentioned, and describe their differences in as much detail as possible. Which one was used in this lab demonstration?
Answer: The three different types of chromatography are (1) the stationary phase is the support on which the chromatography is performed (Thinkwell,2012). The stationary phase is part of the chromatographic system where the mobile phase flows, this is where the distribution of the solutes that occur between phases. This can be solid or a liquid that is immobilized or absorbed on a solid. The stationary phase may also consist of particles, it could be a fibrous material or it could be the walls of a tube (Library4science, 2012).
(2) this is the mobile phase where the moving of solvent front for which carries the mixture (Thinkwell, 2012). This system is used to carry the solutes through the stationary phase. The mobile phase can be either liquids or gases. The liquid mobile phase are use to adjust the chromatography separation and retention in liquid chromatography. The temperature of the gas mobile phase is used to adjust the retention in gas chromatography (Library4science, 2012).
(3) The substrate is the mixture being separated. An example would be grape drink can be separated by the use of TLC (Thinkwell,2012).
References:
www.thinkwell.com accessed on October 2,2012.
"Copyright © 2000-2008 Library4science.com, LLC." N.p., n.d. Web.
(b) (2 pts.) How did chromatography get its name, and how is it used differently now compared to in the past (according to the video)? What is it and how does it work?
Answer: The name chromagraphy was used because of the techniques that were originally developed to separate colored compounds. The modern chromagraphy allows for the separation of the compounds based on their properties (Thinkwell, 2012).
Reference:
www.thinkwell.com accessed on October 2,2012.
(c) Suppose I melted a green popsicle and ran a chromatogram of the resulting substrate.
(1 pts.) In the simplist case, what would I expect to see? Include as much
detail as possible.
Answer: If you wanted to see if the green popsicle had green coloring in them, then you would need to take two drops of the popsicle and place it on a filter paper. In a beaker make sure that the baseline is above the solvent of water. The phase that you are trying to do is the substrate phase where a mixture is trying to be separated. So the distance moved by the green popsicle is the distance from the baseline to the center of the smear at the end of the chromatography. So the Rf values would be calculated by dividing the distance of the popsicle sample moved by the distance the solvent front moved (Thinkwell,2012,and experiment).
[ii] (4 pts.) Suppose that the dot/area representing the longest wavelength of
color in this situation was located 29 mm from the baseline, and the dot/area
representing the shortest wavelength of color was located 44 mm from the
baseline (see Figure 9.4 on page 288 for help). If the solvent traveled 65 mm
from the baseline, what was the Rf for each of these two components of the
sample?
[SHOW ALL WORK]
Answer: The Rf = the distance spot moved___
the distance solvent moved
so it would be 29mm = 0.45
65mm
And 44mm = 0.68
65mm
[iii] (2 pts.) What does this mean? Why, in this case, would one component of the sample travel farther than the other? What's going on here—what causes this to happen?
Answer: The separation in TLC is based on differnences in polarities. Since water is a polar molecule, while the molecules making up the filter paper are non polar. So the blue pigment is more polar than the yellow, and this is more soluble in water than on the surface of the filter paper. So bluepigment travels further (Thinkwell, 2012).
(d) (2 pts) What is the difference between the stationary phase and the mobile phase as it relates to this lab? What was the stationary phase in this demonstration? What was the mobile phase in this demonstration?
Answer: The difference between the stationary phase and the mobile phase is that the stationary phase is support on which the chromography is preformed. The mobile phase is the moving fronts of which carry the mixture. For the demonstration given the stationary phased used was the filter paper and the mobile phase demonstration was the grape drink (Thinkwell, 2012).
Reference:
www.thinkwell.com accessed on October 2,2012.
Part 2
9.1.3 CIA Demonstration: Conductivity Apparatus-Ionic versus Covalent Bonds
After you watch the above video, answer the questions below in sufficient detail:
(a) (1 pts.) Please state in the blanks provided whether the following samples from the lab were an electrolyte or a nonelectrolyte:
Pure water: _ nonelectrolyte _ Drain cleaner: electrolyte __
Ethanol: _ nonelectrolyte _ Sucrose: _ nonelectrolyte _
Sodium chloride: _ electrolyte _
(b) (2 pts.) Explain your answers to (a) above detail according to what you witnessed in this lab demonstration. What is the evidence for each? How did you arrive at your answers? What does the type of chemical bond have to do with this? Be specific.
Answer:
Some ionic compounds that dissolve in water have the ability to conduct electricity. (i.e Sodium chloride) Sodium Hydroxide and Sodium Hyperchloride are both ionic compounds. When added to water, they separate to form free ions, therefore, conduct electricity. This is evident by the fact that the light bulb lit up. (ThinkWell, 2012)
c) (3 pts.) If you have ever been to a public pool, you know that you are required to exit the pool when there is lightning in the sky. But consider your results from part (a) above and what you learned in this lab, paying particular attention to the very first demonstration that the instructor shows you regarding the light bulb. Does this protocol make sense in light of the data from this demonstration, or is it contradictory? Why or why not? We are talking about water, here, right? Is there anything else going on in this case, chemically speaking, that would change the way we look at this situation?
Answer: Purified water, with no contaminants at all in it, does not conduct electricity to an appreciable degree because water does not ionize into H+ and OH- to a sufficient degree to transport charges well. In other words, pure water does not conduct electricity but tap water does because it still has some salt (or other impurities) in it that allow electrons to move more freely because sodium and chloride disassociate into ions in the water which creates charges and allows the electricity to travel via these charges.
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