4.2.2 Fick’s Laws of Diffusion Quiz
Description
There now follows a quiz relating to the topic, Fick’s Laws of Diffusion.
The quiz is designed to test your recall and knowledge of this topic and may be used at a later date as a revision aid.
Question 6 is experimental within the ASDC VLE course. This question is not compulsory and is not graded. It will not count to any final mark. It will show as being worth 1 mark within the quiz but please ignore this (the pass threshold has been adjusted accordingly). It is included as an opportunity for you to test yourself and get some practice at presenting slightly longer answers, similar in style to the Section B questions that you will encounter in the exam. If you do answer questions 6, your uploaded document will be read and feedback will be provided, if you indicate that this is what you would like.
If you do upload an answer for question 6, please would you;
- Upload the document(s) as .pdf files
- Put your name in the document(s)
- Indicate within the document(s) if you would be willing to share and/or discuss with other students who have submitted answers to the same question.
4.2.2 Fick’s Laws of Diffusion Quiz
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Question 1 of 6
1. Question
1 point(s)Select the appropriate elements against the criteria.
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- Rate of flow of dye molecules, per unit area of matter, occurs at a constant rate. Concentration gradient, dc/dx = constant. Where dc = change in concentration and dx = distance (or length).
- Rate of diffusion of dye molecules is a function of time. Here dc/dt cannot = zero. Where dc = change in concentration and dt = change in time. This also means that dc/dx varies with time.
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Steady State
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Non-steady State
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Question 2 of 6
2. Question
5 point(s)Fill in the missing words. (6 points)
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As dyeing proceeds the concentration of dye in the dyebath , whilst at the same time, dye concentration in the fibre . Fick’s law does not describe how the concentration of dye molecules changes as a function of . Fick’s law describes the accumulation of diffusant (dye molecules) within the fibre at any given point as a function of time and is therefore more relevant to the non-steady state conditions encountered in a practical dyeing situation.
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Question 3 of 6
3. Question
4 point(s)Match the elements with the most appropriate terms from the following equation. (4 points)
J = -D (dc/dx)
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- Diffusional flux (i.e. amount of "stuff" – e.g. mass of dye molecules) diffusing per unit area, per unit time.
- Change in concentration of dye molecules.
- Distance, or path length.
- Diffusional co-efficient (diffusivity). This is a measure of the diffusing properties of the dye and the permeability of the material through which the dye diffuses.
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J
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dc
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dx
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D
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Question 4 of 6
4. Question
4 point(s)Match the “units” with the correct term, as defined in the equation, J = -D (dc/dx).
(4 points)
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J
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c
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x
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D
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The units should “balance-out” at each side of the equation.
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Question 5 of 6
5. Question
1 point(s)Match the answers to the most appropriate term. (1 point)
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- Distance from the fibre surface where the local velocity of dye molecules reaches ~99% of those in the bulk solution.
- Layer in which the molecular diffusion of dye molecules in the liquor has a big influence on the rate at which dye molecules reach the surface of the fibre.
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Hydronamic Boundary Layer
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Diffusional Boundary Layer
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Question 6 of 6
6. Question
1 point(s)Explain, in 2-3 paragraphs, and illustrating your answer with equations or graphs where necessary, the relevance and effect of temperature on the rate of dye diffusion.
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Upload your answer to this question.
This response will be reviewed and graded after submission.
Grading can be reviewed and adjusted.Grading can be reviewed and adjusted.Hint
Consider the effect of temperature on the average molecular kinetic energy associated with dye molecules.
Mention the relevance and consequence of thermodynamic parameters, e.g. ΔH (enthalpy of dyeing)
Mention the Arrhenius relationship, its relevance and the usefulness of a log plot to find values of “Ea” (activation energy of diffusion)
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