Projects

Karl Fischer Titrations- Applying Fundamental Chemical Principles

Name: Carly Baumann                                                                     Date: October 28, 2014

Lab Partner’s Name: Heidi Tubbs

Lab Instructor: David Morris

LABORATORY WRITTEN WORK

OBJECTIVE

The objective of this experiment is to perform redox reactions, while observing the effects of shifting the equilibrium in a reaction using Le Châtelier’s P. Karl Fischer Titration will be used to learn the basics resistivity and ion conductivity. The experiment was done to determine the content of water in hand sanitizer.

EXPERIMENTAL METHOD

Materials

All solutions were prepared in the laboratory or came from the Virginia Tech Library. The chemicals used were Cu(NO3)2, FeSO4, Pb(NO3)2, Zn(NO3)2, AgNO3, CoCl2, and HCl. The metals used were Cu, Fe, Pb, and Zn.

Synthesis

Part 1. Redox Reactions and Their Physical Effects

Four pre-labeled strips of Cu, Fe, Pb, and Zn are added to separate wells into each of the four chemicals: Cu(NO3)2, FeSO4, Pb(NO3)2, Zn(NO3)2. After five minutes, the interaction with the solution was observed and noted.

Part 2. Equilibrium: Le Châtelier’s Principle

Observations are taken after each step. CoCl2 is added to a drop of water, then HCl is added until a change is noticed. Water is then added until the solution turns purple and the test tube is poured to make two halves of the solution. One drop of AgNO3 is added to the first test tube. The other test tube is placed in a hot water bath until a change is noticed; then the test tube is placed in an ice bath.

Part 3. Discovering the Conductivity of Different Solutions

The prepared and labeled solutions were measured for their resistivity. The distance of the electrodes were measured and made sure to be the same distance apart for each solution. Conversion calculations were made and calculated to find the conductivity of the solutions.

Part 4. Using a Karl Fischer Titration to Determine the Water Content of a Substance

5mL of methanol was added to a vial of 1.6g of hand sanitizer and is shaken until it is a homogeneous solution. 100uL of the solution is then added to the titrator. After the titration is complete, the mass percent of water was in the solution.

EXPERIMENTAL DATA

  Cu(NO3)2 FeSO4 Pb(NO3)2 Zn(NO3)2
Cu(s) ·      Appears to have very little difference·      Appears shinier ·      Appears to have very little difference·      Appears shinier ·      Appears to have very little difference·      Appears shinier ·      Seems to have gotten slightly darker
Fe(s) ·      Liquid turned green like color·      Metal a dark color with copper spots ·      Metal turned a darker grey color ·      Flakes appear to form at the top·      Turns dark grey ·      Slightly darker grey·      Flakes form
Pb(s) ·      Black material coming off the metal·      Black flack substance ·      Metal turns darker grey color ·      Metal turns darker grey color ·      Metal turns darker grey color
Zn(s) ·      Bubbles formed off the metal·      Turned dark grey ·      Turned dark grey ·      Particles forming off the metal·      Crystal like flakes forming ·      Slightly darker grey color

Table 7-1. Grid and Observation Table for Redox Reactions

Resistance:

                        Peo solution with LiCl (Ω): 6

Peo solution: 100

DI water: ∞

DI Water Peo Solution Peo Solution with LiCl
Resistivity(Ω * m) 0.570 0.0342
Conductivity(s/m) 0 1.75 29.24
Conductivity(μs/cm) 0 17500 292400

Table 7-2. Recorded and Calculated Values of DI Water, PEO Solution with LiCl Salt

Mass of Dry Scintillation Vial: 13.40g

Mass of Hand Sanitizer: 1.66g

Mass %: 7.26%

Group 9 Mass %: 11.76%

Group 11 Mass %: 9.8%

Average %: 9.61%

Standard Deviation %: 2.26%

% H2O (undiluted hand sanitizer): 32.77%

OBSERVATIONS

The observations of part one of this experiment are located in Table 7-1.

Part two observations: When added to the test tube, the CoCl2 is a purple-blue color. When the deionized water is added, the solution turns pink. When HCl is added, the solution turns a blue like color. When AgNO3 is added, the solution turns lavender with white specs in it. When added to the heat bath, the solution turned dark blue. After being put into the ice bath, the solution turns back to a pink color.

SAMPLE CALCULATIONS

The calculations provided below show the calculations needed to complete this experiment. The calculations included determined the average percent mass of water in the hand sanitizer. The calculations also determined the average percent mass of water in the sample. The calculations allowed for the standard deviation percent to be found using excel.

Average % mass of water in the sample:

(11.76%)(7.26%)(9.8%)/(3)= 9.61%

% H2O (undiluted hand sanitizer):

=32.77%

Standard Deviation Percent was performed using excel: 2.26%

RESULTS AND DISCUSSION

After observing the changes that occurred from different metal strips in different solutions, it was noted that some did not go through any change at all, whereas others had noticeable difference after just five minutes. When zinc was put in lead (II) nitrate, crystals were formed on the lead, so there was a metal displacement. This is because zinc is more reactive than the lead from the solution of lead (II) nitrate. Many reactions for part 1 had rust, meaning that there was a redox reaction. For example, the reaction between copper (II) nitrate and iron, rust was formed. This is because iron displaced the copper since it’s more reactive, and as a result, iron nitrate solution is formed along with solid copper.

For part two of the experiment, the observations were qualitative in nature, because it was to look at the change in the solutions after something was added. When water was added to the cobalt (II) chloride, the solution turned light pink when the color in the beginning was light purple. This is because of the change in concentration for the chloride ion, but another option could be due to the change of temperature, which is what Le Châtelier’s Principle also says. When HCl was added, the color turned into a dark blue. This is because there would be an excess of chlorine ions that would be added, since there is already chloride in the cobalt (II) chloride, from the beginning. The solid silver chloride would be formed if silver nitrate was added, and as a result, white flakes appear in the solution. The solution turns blue after you put it in hot water because when the temperature increases, the equilibrium shifts to the right, making more blue ions rather than being pink, but when you put it back in the cold water (the ice bath, in this case), the color changes back to light pink because the equilibrium shifts back to the left and the temperature decreases.

For part three of the experiment, resistivity is measured for three different solutions. In this case, PEO solution with LiCl had a different value compared to the distilled water and PEO solution because the PEO has a highly polar nature and it can bind many ionic salts and/or electrolytes so that conductivity is there, and when you mix this with LiCl, this makes it reactive compared to the other metals.

For part four of the experiment, where a Karl Fischer Titrator was used to determine the water content of a substance, the main point was to observe the reaction between the iodine and water, where after all the water has been reacted, the color of iodine comes, which would be brownish-yellow.

EXPERIMENTAL UNCERTAINTY

The glassware that used in this experiment has uncertainties. The beaker, pipet, and graduated cylinder all have an uncertainty of +/- 0.01. The glassware used could have affected the experiment anytime if read incorrectly. This would change the results of the chemicals calculated.

POST-LABORATORY QUESTION

Part 1-Redox Reactions and Their Physical Effects

Some participated in the redox reaction and some did not because it depended on where the substances are located on the reactivity table. For example, when zinc was put in lead (II) nitrate, crystals were formed on the lead. This is because zinc is more reactive than the lead from the solution of lead (II) nitrate, which can be determined from the reactivity series. This reaction would be shown. Another example would be a reaction between copper (II) nitrate and iron where rust was formed. This was because iron displaced the copper since it’s more reactive, and as a result, iron nitrate solution is formed along with solid copper.

Part 2-Equilibrium: Le Châtelier Principle

When water was added to the cobalt (II) chloride, the solution turned light pink when the color in the beginning was light purple. This is because of the change in temperature of the water. When HCl was added, the color turned into a dark blue, and in this case, the concentration would change because of the chlorine ions that were added. Silver chloride also changes the equilibrium because of the chloride ions that are added, just like HCl in the previous step. When you put the solution in hot water the temperature increases, but when put back in the cold it turns back to light pink because of the shift to the left as temperature decreases.

Part 3- Discovering the Conductivity of Different Solutions:

Tap water has ions for the soil in the water, but DI water is pure water molecules or as close as you can get to pure water molecules. This affects the conductivity and resistivity because there are traces of ions in the tap water. Although not a huge difference, this can still affect the results in an experiment.

Part 4-Using a Karl Fischer Titrator to Determine the Water Content of a Substance:

Redox reactions are used in a Karl Fischer Titrator because of the redox reaction from iodine, which then determines the water content in the sample. Conductivity is used in a Karl Fischer Titrator for the measurement of water because of the double platinum electrode that is there.

CONCLUSION

There were four parts to this experiment, where the main focus was to learn about the different effects on a reaction when shifting its equilibrium. The other focus is using the Karl Fischer Titration in general chemistry.

REFERENCE

[1]Activity Series. http://www.cod.edu/people/faculty/jarman/richenda/1551_hons_materials/Activity%20series.htm. (Accessed: 24 October 2014)

[2] Amateis, Patricia; Long, V; Dalton, M. General Chemistry 1045 Laboratory Manual, 1/ed. Blacksburg, Virginia: Virginia Tech

Moss Beach Field Study 2/6/14

Meiosis Project

A normal cell has 2N chromosomes. We use N because the number of chromosomes change through out different species. During Interphase I, the chromosomes replicate its 2N to produce a 4N cell. Then in Prophase I, the nuclear membrane disappears and the chromosomes start “crossing over.” Crossing over is when the genes randomly exchange information with another chromosome. This is only done in meiosis because in mitosis the goal is to create two identical cells. In meiosis the crossing over allows for siblings to be different from one another. If crossing over did not occur, siblings would all be identical. The next step is Metaphase I. This is when the tetrads align up in the middle of the cell. The centriole has moved to opposite poles of the cell. Following Metaphase, Anaphase I is when the spindle fibers break the tetrads to the poles of the cell. The cell reform and there are two cells now that consists of 2N in Telophase I and Cytokinesis. Each chromosome still consists of two chromatids, but they are no longer identical because of the crossing over. The cycle begins again with Prophase II. This time the chromosomes are not replicated, so there is only 2N. In this cycle the spindle fibers form again. The chromosomes align in the middle again and the centrioles move to opposite pole in Metaphase II. However crossing over does not occur because the chromosomes do not make contact with each other. The chromosomes are not called tetrad’s because there are only two chromatids instead of four. In Anaphase II, the spindle fibers pull apart the chromatids to the opposite poles. Finally in Telophase II and Cytokinesis, the cell walls reform and now there are four daughter haploid cells. They are called haploid because each cell only has one chromatid instead of two, or 1N instead of 2N.

I worked on my project with Serena. You can find her post at her blog under projects. Her blog is exploredreamexamine.wordpress.com. I found this project helpful, because as I was doing the project, I was also learning about meiosis. It also helped me learn the differences between mitosis and meiosis. I thought the project was also a lot of fun because it was new experience for me. I have never done a motion picture with actual still pictures. It was nice working with Serena because she was a lot of fun and made learning the information fun. It was good to be able to work with someone and learn from each other.

I hope this information has helped teach you about meiosis and a little about the differences between mitosis and meiosis. Remember KEEP CALM AND LEARN ON.

Linked below is a prezi about defects on photosynthesis in plants.

Click here to see the prezi

I hope this has helped you learn more about how diseases can affect photosynthesis in plants. Remember KEEP CALM AND LEARN ON.

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