Aha! Chemistry with Prof Bob
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  • LEARNING MODULES
    • Chapter 02 Stuff, matter: What is it? >
      • 0200 Stuff, matter: A theory of atoms
      • 0201 Atoms: The building blocks of all stuff
      • 0202 People classifying stuffs. Why?
    • Chapter 05 Chemical reactions and chemical equations >
      • 0500 Chemical reactions and chemical equations. Overview
      • 0501 Chemical amount and its unit of measurement, mole
      • 0502 The Avogadro constant: How many is that?
      • 0503 The Avogadro constant: Why is it that number?
      • 0504 Chemical formulas: What can they tell us??
      • 0505 Chemical equations: What can they tell us?
      • 0506 Limiting reactants: How much reaction can happen?
      • 0507 Balanced chemical equations: What are they?
      • 0508 Chemical reactions as competitions
    • Chapter 09 Aqueous solutions >
      • 0901 What is a solution? And what is not?
      • 0902 Miscibility of liquids in each other
      • 0903 Like dissolves like? Shades of grey
      • 0905 Dissolution of ionic salts in water: A competition
      • 0906 Can we predict solubilities of salts?
      • 0907 Solution concentration
      • 0908 Chemical species, speciation in aqueous solution
      • 0909 Solutes: Electrolytes or non-electrolytes?
      • 0910 Electrolytes - strong or weak?
      • 0911 Concentrated, dilute, strong, weak
      • 0912 Species concentration vs. solution concentration
      • 0913 Weak electrolytes: Getting quantitative
    • Chapter 11: Dynamic chemical equilibrium >
      • 1100 Dynamic chemical equilibrium: Overview
      • 1101 Visualising dynamic chemical equilibrium
      • 1102 The jargon of chemical equilibrium
      • 1103 Equilibrium constants: The law of equilibrium
      • 1104 The law of equilibrium: an analogy
    • Chapter 22 Evidence from spectroscopy >
      • 2200 Spectroscopy: Overview and preview
      • 2201 Quantisation of forms of energy
      • 2202 Light: Wave-particle "duality"
      • 2203 Ultraviolet-visible spectroscopy
      • 2204 Beer’s law: How much light is transmitted?
    • ENVIRONMENTAL CHEMISTRY >
      • EARTH'S ATMOSPHERE >
        • Chapter 27 The greenhouse effect, climate change >
          • 2700 The greenhouse effect: overview
          • 2701 Is Earth in energy balance?
          • 2702 CO2 in the atmosphere before 1800
          • 2703 So little CO2! Pffft?
          • 2704 Does CO2 affect Earth's energy balance?
          • 2705 The "greenhouse effect"
          • 2706 Why does CO2 absorb radiation from Earth?
          • 2707 The "enhanced greenhouse effect"
          • 2708 Why doesn't CO2 absorb the radiation from the sun?
          • 2709 Why are N2 and O2 not greenhouse gases?
          • 2710 Doesn't water vapour absorb all the IR?
          • 2711 Carbon dioxide from our cars
          • 2712 The source of energy from combustion
          • 2713 Comparing fuels as energy sources
          • 2714 Methane: How does it compare as a GHG?
          • 2715 Different sorts of pollution of the atmosphere
          • 2716 "Acidification" of seawater
      • FUELS
      • EARTH'S OCEANS AND WATERWAYS
  • TEACHERS' CORNER
    • TC01 Language and meaning in chemistry >
      • TC0101 The jargon we use
    • TC02 REPRESENTATION IN CHEMISTRY
    • TC03 MODELLING IN CHEMISTRY
    • TC04 KNOWING AND LEARNING
    • TC05 Communicating chemistry >
      • TC0501 Overview, preview
    • TC06 COMPLEXITY of LEARNING CHEMISTRY
    • TC07 PEDAGOGOICAL CONTENT KNOWLEDGE, PCK >
      • TC0701 Amnesia of the chemistry teaching professioN
    • MODULE-SPECIFIC PCK >
      • Chapter PCK11 Dynamic chemical equilibrium >
        • PCK1101 Visusalizing dynamic chemical equilibrium
        • PCK1103 Equilibrium constants: The law of equilibrium
      • Chapter PCK22 Evidence from spectroscopy >
        • PCK2204 Beer's law
  • NAVIGATION
    • Table of contents
    • Index, alphabetical
Module 1101

Visualising dynamic chemical equilibrium

What is dynamic about chemical equilibrium?

What does it mean for a reaction to go 'both ways' simultaneously?

Is it a useful mental picture to visualise just one ion/molecule of each of the reaction participants - as you might (wrongly) interpret the equation?

The answer is definitely not! Why not?

Visualise the many molecules of species in the reaction mixture, rather than focus on the reaction equation.

Competition, competition ... always competition. Imagine that you are the species being competed for.

What governs how far reaction goes to reach dynamic chemical equilibrium?




An analogy
​

​What is the condition of dynamic chemical equilibrium? What does it mean that the “forward reaction” and the “backward reaction” occur simultaneously and at the same rate? Prof Bob’s analogy might help to clarify meaning.
Did this analogy help your insight into what is going on in a reaction mixture with trillions upon trillions of ions or molecules of each of the reaction species?
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KEY IDEAS - Visualising dynamic chemical equilibrium
​

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We can't see change, but there is so much going on. A very dynamic situation. (But not an equilibrium situation)

Forewarning

Interpreting the language used by chemists is often a problem for those learning chemistry. To a student, the meaning of a phrase or term used by a chemist might be completely misleading. He/she knows what they mean when they use the language of the profession, but until you are familiar with this language, potential trouble looms. This is especially the case in regard to the topic of dynamic chemical equilibrium.

Prof strongly urges you to go to Module 1102 The jargon of chemical equilibrium in conjunction with your sense-making of this module.

You might even find it useful to think about communication in a more general sense by looking at Module 2703 The jargon we use. Are talker and listener on the 'same page'? Is the talker making presumptions about your understanding of words and phrases? Of course, we do that all the time, even in everyday conversations, but it is useful if the presumption is close to correct!



The conditions of chemical equilibrium in a reaction mixture

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​Chemical reactions as competitive processes

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Beware! This representation might suggest that chemical equilibrium is the result of one A and one B competing for a single H+ ion. No, no, no! That might be the case in a single collision between AH and B (or between BH and A), but there are trillions upon trillions of such collisions happening all the time. To visualise a reaction mixture, you need to try to picture the overall result arising from these many many collisions happening every moment.

Changing relative amounts of 'reactants' and 'products'

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​Visualise yourself as the object of competition

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NOTE TO TEACHERS

For some thoughts about  pedagogical content knowledge related to this concept, see Teachers' Corner page
PCK1101: Visualizing dynamic chemical equilibrium.
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SELF CHECK - Some thinking tasks

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If you want to understand dynamic chemical equilibrium, visualise those trillions and trillions of molecules and ions bumping into each and competing for some chemical species. Don't look at the reaction equation for this purpose.
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Finding your way around .....

You can browse or search the Aha! Learning chemistry website in the following ways:
  • Use the drop-down menus from the buttons at the top of each page to browse the modules chapter-by-chapter.
  • Click to go to the TABLE OF CONTENTS (also from the NAVIGATION button) to see all available chapters and modules in numbered sequence.
  • Click to go to the ALPHABETICAL INDEX. (also from the NAVIGATION ​button).
  • Enter a word or phrase in the Search box at the top of each page.

​Seek wisdom, insight and understanding. Satisfaction will follow.
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LEARNING CHEMISTRY FOR UNDERSTANDING

Email: [email protected]


​© The content on any page in this website (video, text, original images, and self-check) may be used without charge for non-commercial educational purposes, provided that acknowledgement is given to the Aha! Learning Chemistry with Prof Bob website, with specification of the URL: https://www.ahachemistry.com/​
  • HOME
    • TALK WITH PROF BOB?
  • LEARNING MODULES
    • Chapter 02 Stuff, matter: What is it? >
      • 0200 Stuff, matter: A theory of atoms
      • 0201 Atoms: The building blocks of all stuff
      • 0202 People classifying stuffs. Why?
    • Chapter 05 Chemical reactions and chemical equations >
      • 0500 Chemical reactions and chemical equations. Overview
      • 0501 Chemical amount and its unit of measurement, mole
      • 0502 The Avogadro constant: How many is that?
      • 0503 The Avogadro constant: Why is it that number?
      • 0504 Chemical formulas: What can they tell us??
      • 0505 Chemical equations: What can they tell us?
      • 0506 Limiting reactants: How much reaction can happen?
      • 0507 Balanced chemical equations: What are they?
      • 0508 Chemical reactions as competitions
    • Chapter 09 Aqueous solutions >
      • 0901 What is a solution? And what is not?
      • 0902 Miscibility of liquids in each other
      • 0903 Like dissolves like? Shades of grey
      • 0905 Dissolution of ionic salts in water: A competition
      • 0906 Can we predict solubilities of salts?
      • 0907 Solution concentration
      • 0908 Chemical species, speciation in aqueous solution
      • 0909 Solutes: Electrolytes or non-electrolytes?
      • 0910 Electrolytes - strong or weak?
      • 0911 Concentrated, dilute, strong, weak
      • 0912 Species concentration vs. solution concentration
      • 0913 Weak electrolytes: Getting quantitative
    • Chapter 11: Dynamic chemical equilibrium >
      • 1100 Dynamic chemical equilibrium: Overview
      • 1101 Visualising dynamic chemical equilibrium
      • 1102 The jargon of chemical equilibrium
      • 1103 Equilibrium constants: The law of equilibrium
      • 1104 The law of equilibrium: an analogy
    • Chapter 22 Evidence from spectroscopy >
      • 2200 Spectroscopy: Overview and preview
      • 2201 Quantisation of forms of energy
      • 2202 Light: Wave-particle "duality"
      • 2203 Ultraviolet-visible spectroscopy
      • 2204 Beer’s law: How much light is transmitted?
    • ENVIRONMENTAL CHEMISTRY >
      • EARTH'S ATMOSPHERE >
        • Chapter 27 The greenhouse effect, climate change >
          • 2700 The greenhouse effect: overview
          • 2701 Is Earth in energy balance?
          • 2702 CO2 in the atmosphere before 1800
          • 2703 So little CO2! Pffft?
          • 2704 Does CO2 affect Earth's energy balance?
          • 2705 The "greenhouse effect"
          • 2706 Why does CO2 absorb radiation from Earth?
          • 2707 The "enhanced greenhouse effect"
          • 2708 Why doesn't CO2 absorb the radiation from the sun?
          • 2709 Why are N2 and O2 not greenhouse gases?
          • 2710 Doesn't water vapour absorb all the IR?
          • 2711 Carbon dioxide from our cars
          • 2712 The source of energy from combustion
          • 2713 Comparing fuels as energy sources
          • 2714 Methane: How does it compare as a GHG?
          • 2715 Different sorts of pollution of the atmosphere
          • 2716 "Acidification" of seawater
      • FUELS
      • EARTH'S OCEANS AND WATERWAYS
  • TEACHERS' CORNER
    • TC01 Language and meaning in chemistry >
      • TC0101 The jargon we use
    • TC02 REPRESENTATION IN CHEMISTRY
    • TC03 MODELLING IN CHEMISTRY
    • TC04 KNOWING AND LEARNING
    • TC05 Communicating chemistry >
      • TC0501 Overview, preview
    • TC06 COMPLEXITY of LEARNING CHEMISTRY
    • TC07 PEDAGOGOICAL CONTENT KNOWLEDGE, PCK >
      • TC0701 Amnesia of the chemistry teaching professioN
    • MODULE-SPECIFIC PCK >
      • Chapter PCK11 Dynamic chemical equilibrium >
        • PCK1101 Visusalizing dynamic chemical equilibrium
        • PCK1103 Equilibrium constants: The law of equilibrium
      • Chapter PCK22 Evidence from spectroscopy >
        • PCK2204 Beer's law
  • NAVIGATION
    • Table of contents
    • Index, alphabetical