lab004_diffusion01

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School

Mercer County Community College *

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Course

101-030

Subject

Chemistry

Date

Jan 9, 2024

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doc

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Uploaded by ProfHamsterPerson881

Experiment 1 - Molecular Weight and Diffusion Rate Molecular weight is an indication of the mass and size of a molecule. The purpose of this experiment is to determine the relationship between molecular weight and the rate of diffusion through a viscous medium . You will investigate two dyes. Molecule Molecular weight Blue Dye Solution 793 grams/mole Red Dye Solution 496 grams/mole Materials Red and Blue Dye Solutions 1 Bottle of Corn Syrup 1 – cm Petri Dish (top and bottom halves) Stopwatch or Timer Small plastic metric ruler White piece of paper, index card, or white paper towel * * you provide Procedure 1. Take the petri dish and fill both halves with corn syrup until about ½ - ¾ of the way to the top. Place one half on top of a white piece of paper. Place the small clear plastic ruler under the dish 3. Place a single drop of blue dye in the middle of the corn syrup, 4. Note the position where the dye fell by reading the location on ruler. 5. Measure the diameter of the dye (the distance across the widest part of the circle) after ten seconds and 20 seconds. Record your data in Tables 1 and 2. 6. Repeat steps 3 – 5 using the red dye. 7. NOTE: You must shake the dyes very well immediately before the experiment. Table 1: Rate of Diffusion in Corn Syrup Time (sec) Blue Dye Red Dye 10 20 (data table – worth 2 points)

At this point, PHOTOGRAPH YOUR WORK. Submit the image along with this worksheet to the assignment drop box in the course. You must include your totem or student ID to receive credit. (2 points) Questions (worth ½ point each) 1. Which dye diffused the fastest after 10 seconds? The red dye diffused more rapidly than the blue dye after 10 seconds because it has a lower molecular weight. 2. Does the rate of diffusion correspond with the molecular weight of the dye? The rate of diffusion of a dye is correlated with its molecular weight. Dyes with lower molecular weights diffuse more quickly than dyes with higher molecular weights. 3. Does the rate of diffusion change over time? The rate of diffusion also changes over time. In the beginning, the dye is concentrated in a small area, so the concentration gradient is high. This means that the dye molecules are moving very quickly to try to equalize the concentration. However, as the dye molecules spread out, the concentration gradient decreases, and the rate of diffusion slows down.

4. If the dishes were left to sit overnight, the next morning would you expect the diameter of the dye to be similar or different? After overnight diffusion, the diameters of the two dye spots would be similar. This is because both dyes would have had enough time to diffuse to their equilibrium concentrations. The red dye would still have diffused slightly faster than the blue dye, but the difference would be small.

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