Virtual Experiment 25

SOLUTIONS

The following discussion and videos can be used to complete for Virtual Experiment 25 laboratory assignment

The assignments that must be completed are:

Complete the pre laboratory writing assignment before the lab sessions begins.
Complete the pre laboratory problems before coming to the class meeting.
Using the class data provided in the experiment to complete ALL trials of Part 1. Determine the concentration of the potassium sulfate solution, for each trial given in the class data.
Conclusion paragraph

Experiment 25

This is the presentation of the experimental theory and procedure

ch13 unit2.mp4

This is a presentation of the theory of concentration

Discussion

Solution Concentrations. Solutions are homogeneous mixtures that contain a solute and solvent. The amount of the solute that dissolves in the solvent is dependent on many factors including temperature, pressure and structure of the substances. In general, the solute is more likely to be soluble or miscible if the polarities are similar, “like dissolves like”; however, the solubility rules for ionic compounds often help us understand which solutes are more soluble in water solutions. The solubility of a compound in the solvent is defined as the

Solubility = grams of solute per 100 mL of solvent

The density and composition of a solution are also related to the amount of the solute present. These terms, however, do not quantitatively define the exact amount of solute present. For this, several numerical values are used to define the concentration of the solution. Generally, these values define the amount of solute present in the amount of solvent present in mass, moles or volume. The definitions of each concentration provide the basis for calculations with specific units.

Experiment 25 Discussion

Paper chromatography. Chromatography can be thought of as a dynamic extraction where the solute continually has an option of two phases. This is accomplished by having one phase move by a stationary phase. Chromatography was discovered by Michael Tswett (a Russian botanist) early in the 20th century. Tswett allowed a mixture of pigments extracted from plants to percolate down through a column of calcium carbonate. Solvent was added from the top as needed to cause continuous movement of the pigments down the column. Pigments that were more strongly attracted to the stationary phase (calcium carbonate) and had less affinity for the solvent (moving phase) moved down the column more slowly than pigments that had greater affinity for the solvent and had weaker attraction for the stationary phase. Tswett observed that the pigments had separated into several differently colored bands as a result of the fact that they moved down the column at different rates. The term chromatography was coined to describe the phenomenon.

Pre laboratory Writing

Complete the pre laboratory writing assignment in your laboratory notebook. The prewriting must be completed before the laboratory session begins. The writing should include a purpose/hypothesis of the experiment, a discussion or theory, a detailed step by step summary of the procedure explaining what data will be collected and how you will collect it. Data Tables or space to collect the data should be included within the procedure discussion. Look up any SDS on chemicals that you are not familiar.

Pre laboratory Problems

Complete the pre laboratory problems before coming to the class meeting.

To find the information about each of the ionic solids, you can some information in Appendix A and Appendix L, Wikipedia, or an SDS for the ionic compound.

lab 25 pre lab question

Question 7 - Simulation of separation of Red and Blue ink

Read the background at https://amrita.olabs.edu.in/?sub=73&brch=8&sim=133&cnt=1 Using the simulation at https://amrita.olabs.edu.in/?sub=73&brch=8&sim=133&cnt=4 to complete a chromatogram of the separation of Red and Blue ink. The site loads very slowly, have patience. Read the theory and procedure then complete the simulator. Measure and determine the Rf for each ink sample. Take a screen shot of the the final submission of your results.

lab 25 part 2 similation.mp4

You can use this image to measure the distances and calculate the Rf. Try to complete the assignment if you are able to load the program.

Procedure

Part I. Potassium Sulfate Solution

10 mL of an unknown concentration of K2SO4 was weighed and then the water solvent was slowly heated until the water was completely evaporated from the solution. From the mass of dry potassium sulfate remaining and the loss of mass from the evaporated water, the concentration of the solution will be determined.

Use the class data provided to determine the molarity, molality, % mass and mole fraction of each trial.

V-Exp 25 class data

lab 25 part 1 calculations.mp4

This is a video explaining the calculation for Part A of this experiment.

lab 25 graph.mp4

This is a video explaining how to prepare the graph of %mass and density values given in the pre laboratory problems.

Part II. Paper chromatography.

Part A - Simulation of the separation of proteins - Optional

Another simulation of the separation of proteins.

http://www.people.vcu.edu/~elhaij/bnfo300/17/Units/Protein/paper-chromatography.pps

Part B - ACTIVITY - Separation of Black ink - optional

Complete the separation of a black ink pen using these directions: http://swe.mit.edu/outreach/virtual_resources/paper_chromatography.pdf

Part C - Separation of metal cations in a mixture and an unknown - required

Finally using the Metal ion chromatogram below and the step wise chromatograms in the procedure of the full experimental assignment, measure the Rf of each metal ion in the pure samples, the mixture and the unknown sample and determine the metal ions present in the unknown sample. The images of the chromatogram during the various stages of the development are present in the updated experiment document.

lab 25 chromatogram preparation.mp4

This is Dr. Sullivan completing and explaining the laboratory assignment.

Lab 25 Chromatogram of metal ions

this document contains images of the chromatogram at different stages

The following movies explain the theory and how to calculate an Rf.

https://youtu.be/NSJIAcfvEJI

Separation of Components from a Mixture of Red and Blue Inks by Paper Chromatography - MeitY OLabs

https://youtu.be/Ix2GRnKnZas

TLC Lab

Dr. Richard Musgrave

The procedure for separating metal ions using paper chromatography is described.

Report and Conclusion Paragraph

Complete the data and result tables using the class data given above, graphs, calculations and answer all required questions.

Complete a conclusion paragraph using the RERUNS method. A discussion of how to write a conclusion paragraph is given in Appendix D: How to Write a Formal Laboratory Report

Experiment 25 Final Report

Virtual Experiment 25

This is the complete laboratory assignment

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