Aha! Chemistry with Prof Bob
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    • Table of contents
    • Index
    • 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, chemical equations >
      • 0500 Chemical reactions vs. 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 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?
    • Chapter 27 Communicating chemistry >
      • 2700 Overview, preview
      • 2703 The jargon we use
  • TEACHERS' CORNER
    • T01 Communicating chemistry
    • T02 Beer's law
    • T03 Professional amnesia of the chemistry teaching professio
    • T04 Law of equilibrium
    • T05 Visusalizing dynamic chemical equilibrium
    • Information vs. knowledge
  • PERSONAL GALLERY
    • Family
    • Travel
    • Playful dolphins
    • The University of Western Australia
    • Kings Park
    • Perth
    • At work
    • 999 Thermodynamics
Module 1100

​

Dynamic chemical equilibrium: An overview


​What is the notion of dynamic chemical equilibrium?

In what sense is it dynamic?

How best to visualise dynamic equilibrium, at the levels of ions and molecules?

Does this topic have a jargon of its own, that must be understood?


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An overview of the chapter
​

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What a crowd! Everyone bumping into others ..... It's enough to make you think of what's going on in a reaction mixture.
The condition of dynamic chemical equilibrium can be achieved when a reaction is reversible: there can be reaction to form the “products” as well as reaction to form the “reactants”.

​If we refer to a generalized equation for a reversible reaction …
​
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this means that reaction of substances A and B (the “reactants”) to form the substances C and D (the “products”) happens at the same time that C and D react to form A and B.

“Reversibility” is indicated by the double arrow symbol in the chemical equation.

In a reaction mixture in the condition of dynamic chemical equilibrium, the concentrations of reactants and products (and, therefore, the properties of the reaction mixture) do not change as time passes – not because the reaction has gone to completion, nor because nothing is happening, but because reaction forming the “products” is happening at exactly the same rate (in moles per second) as is reaction to form the “reactants”.
​

Opposite and simultaneous reactions can be difficult to visualise. In Module 1101: Visualising dynamic chemical equilibrium, Prof Bob presents a novel way of trying to do so by focussing not on the two reactions, but on whatever is the object of competition that is transferred between substances as the reactions occur.
​
The always-important issue of language is especially significant in this topic because of the large number of terms that are used whose meaning is open to misunderstanding – or at least, ambiguity. These include the terms reactant, product, forward reaction direction, backward reaction direction, shifts to the right, net reaction, shifts to the left, and spontaneous direction of reaction.

 In Module 1102 The jargon of chemical equilibrium 
Prof Bob promotes awareness of the meaning of these terms (and discourages their use as far as possible). We cannot use language terms to communicate meaning unless all of the participants of a conversation understand the terms in the same way.

By the way, you might like to see  Module 2703 The jargon we use where issues of language beyond the topic of chemical equilibrium are brought into focus.
​
Considering the concept of equilibrium quantitatively, it is rather remarkable that in all reaction mixtures (at the same temperature) in which a specified chemical reaction is at equilibrium, there is a particular mathematical expression of species concentrations that has the same numerical value – and this is not the case for any other function of their concentrations.

This paticular function of concentrations is called the reaction quotient (symbol Q). Its numerical value in reaction mixtures at equilibrium is called the equilibrium constant, K.  Prof Bob and Elena conversationally clarify this relationship in Module 1103 Equilibrium constants: The law of equilibrium.


During reaction toward equilibrium the numerical value of Q changes, until equilibrium is achieved when the numerical value of Q is the same as the equilibrium constant appropriate for the temperature of the reaction mixture.

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LEARNING CHEMISTRY FOR UNDERSTANDING

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  • HOME
  • NAVIGATION
    • Table of contents
    • Index
    • 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, chemical equations >
      • 0500 Chemical reactions vs. 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 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?
    • Chapter 27 Communicating chemistry >
      • 2700 Overview, preview
      • 2703 The jargon we use
  • TEACHERS' CORNER
    • T01 Communicating chemistry
    • T02 Beer's law
    • T03 Professional amnesia of the chemistry teaching professio
    • T04 Law of equilibrium
    • T05 Visusalizing dynamic chemical equilibrium
    • Information vs. knowledge
  • PERSONAL GALLERY
    • Family
    • Travel
    • Playful dolphins
    • The University of Western Australia
    • Kings Park
    • Perth
    • At work
    • 999 Thermodynamics