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      • 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?
    • 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
    • Chapter 27 Communicating chemistry >
      • 2700 Overview, preview
      • 2703 The jargon we use
  • TEACHERS' CORNER
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    • T02 Beer's law
    • T03 Professional amnesia of the chemistry teaching professio
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0911 Concentrated, dilute, strong, weak

10/12/2020

1 Comment

 
Module 0911
​

Concentrated, dilute, strong, weak

Does the word concentrated refer to solutions, or to solutes?

And the term dilute?

What about strong, and weak?

Some people use these terms loosely. And wonder why there is confusion!


Preface: It's all about language


Precise use of language can assist understanding. Careless language can cause confusion. ​

In Chemistry, there are terms agreed upon by IUPAC. Particular terms have particular meanings, and we should use them correctly or the receiver of a communication (a listener, or a reader) may become confused, or even develop a wrong understanding of the idea being discussed.

Unfortunately, over the years IUPAC has decided to use terms which have different meaning in everyday life from their meaning in Chemistry. This can be confusing if we don’t recognise which “compartment” (Chemistry, or everyday) that we are operating in.

 
The terms concentrated, dilute, strong, and weak are often used wrongly, because of either lack of care, or ignorance.
​
 
Clarification awaits in this video .....  Aussie is still away.
Prof Bob sets straight the correct usage of the terms concentrated, dilute, strong, and weak
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KEY IDEAS - Concentrated, dilute, strong, and weak 

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On the other side of the bottle is a label that reads "Strong sulfuric acid". Incorrect, and misleading! Why?

Do these terms apply to solutions or to solutes?


​Among the terms concentrated, dilute, strong, and weak, there are two related pairs:

  • Concentrated and dilute are opposite ends of the scale of a property (concentration) of SOLUTIONS.
  • Strong and weak are opposite ends of the scale of a property (extent of ionisation) of SOLUTES.
 
​

Solutions

The concentration of a solutions refers to how crowded the solute species are in the solution – regardless of the volume of solution. See Module 0907 Solution concentration.

We use the following terms:
  • The term concentrated solution refers to solutions with high concentration of solutes (The solute species are very crowded).
  • The term dilute solution refers to solutions with low concentration of solutes (The solute species are widely spaced, on average).

There is no sharp dividing line between concentrations that we refer to as either concentrated or dilute – although it is common to use these terms for solutions whose concentrations are near either extreme.
​
Mostly, these terms are used in a relative sense, such as:
  • A 2 M solution of sucrose in water is more concentrated than a 0.1 M solution of sucrose.
  • A 0.001 M solution of sucrose is more dilute (or less concentrated) than a 0.01 M sucrose solution.
 

Solutes

The terms strong and weak are opposite ends on the scale of extent of ionisation of solutes that are electrolytes (i.e., when the solute dissolves in water, some of the molecules break up into ions). Refer to the previous Module 0909 Solutes: Electrolytes or non-electrolytes?

 And a reminder from a previous Module 0910 Electrolytes: Strong or weak?
  • A solute which is a strong electrolyte: On dissolving in water, all of the solute molecules break up into ions.
  • A solute which is a weak electrolyte: On dissolving in water, only some of the solute molecules break up into ions.
Again, these terms are often used in a comparative sense.

​Here are some examples that show the distinctly different meanings of the two pairs of words: concentrated - dilute, and strong - weak.
  • 10 M HCl solution: A rather concentrated solution of a strong electrolyte.
  • 0.001 M HCl solution: A rather dilute solution of a strong electrolyte.
  • 5.0 M solution of acetic acid: A rather concentrated solution of a weak electrolyte.
  • 0.01 M solution of formic acid: A rather dilute solution of a weak electrolyte
  • 5.0 M solution of sucrose: A rather concentrated solution of a non-electrolyte.
 
​

In summary:
  • Solutions are more or less concentrated (or dilute).
  • Solutes are more or less strong (or weak) electrolytes.

​So, whenever we use any of these four terms, we should think “Am I talking about the solution, or about the solute?”
 It will assist your understanding.



​

Language, language, .......


​If you would like to contemplate a little deeper about the importance of language, and how people communicating need to have matched meaning for words, do go to Module 2703 The jargon we use. Discussion can be not profitable, and/or confusing, if (i) the meanings of terms are different for different people, or (ii) one party is ignorant altogether of the meanings of the terms used.


​
SELF CHECK: Some thinking tasks
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SELF CHECK - Some thinking tasks

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Get it right, now. Recovery of the pathway can be difficult.
1. The following six diagrams are symbolic portrayals, at the level of molecules and ions, of:
  • A concentrated solution of a strong electrolyte solute
  • A dilute solution of a strong electrolyte solute
  • A concentrated solution of a weak electrolyte solute
  • A dilute solution of a weak electrolyte solute
  • A concentrated solution of a non-electrolyte solute.
  • A dilute solution of a non-electrolyte solute.
Water molecules are not shown in the representations.
Decode the symbols for (i) solute molecules, (ii) cations, and (iii) anions, and then decide which of the solutions is represented by each of the diagrams.


Picture
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A
​
B
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C
​
Picture
D
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E
Picture
F



​2.        This questions involves comparison of the three solutions A, B, and C, listed here:
            A         0.20 M aqueous sucrose solution
            B         0.05 M aqueous sucrose solution
            C         0.01 M aqueous sucrose solution
​
(a)        Which one of these solutions is the strongest? Which is the weakest?
(b)        Make some vali
d statements about the relative concentrations of the solutions A, B, and C.
​

3.      Consider the following three aqueous solutions of hypothetical weak electrolytes HX, HY, and HZ.
           A.      0.10 M solution of HA. 11% of the HX molecules are ionised, and 89% remain un-ionised.
          B.      0.10 M solution of HB. 4% of the HY molecules are ionised, and 96% remain un-ionised.
          C.      0.10 M solution of HC. 0.5% of the HZ molecules are ionised, and 99.5 % remain un-ionised.


(a)        Make some valid statements about the relative strengths of the solutes HX, HY, and HZ.
(b)        Why would your ability to answer question (a) be more uncertain if all of the solutions were not 0.10 M?
 
​
4.     Comment on what this person said: “I’m using quite a strong acetic acid solution – it’s 5.0 M. I think that I should use a weaker solution – like 0.01 M”.

​
5.       Consider the following solutions:
Insert appropriate words in the spaces in the following sentences related to the two aqueous solutions A and B:
          A: 0.01 M hydrochloric acid (HCl) solution
          B: 0.08 M acetic acid (CH3COOH) solution.
          C: 0.05 M sucrose (C12H22O11) solution
Insert appropriate terms in the spaces of the text below. Choose from the following words and phrases:
  • concentrated
  • more concentrated
  • less concentrated
  • dilute
  • more dilute
  • less dilute
  • strong
  • stronger
  • weak
  • weaker
  • electrolyte
  • strong electrolyte
  • weak electrolyte
  • non-electrolyte.

​Solution A is more ……...…..…… (that is, less ……........……) than solution B. Solution B is ………......….. than solution C. The solute in solution A is a ………....…...………. electrolyte than the solute in solution B. In fact, because all of the HCl molecules ionise in solution, hydrochloric acid is a …………..…………. . The solute in solution B is a ……....…..……..  because only some of the molecules ……..........… in solution,  but it is a ……..…........…… than the solute in solution C. In solution C, none of the sucrose molecules ionise, so sucrose is called a ….......…....…. .
 


6.   Relational (or Venn) diagrams show the interrelationships among sets of objects or ideas. For example, a relational diagram can portray the relationships such as the following:
  • In one set (category) of dogs (A), all are black. But not all dogs are black.
  • In another set (B), all the dogs have short tails
  • In another set (C), all the dogs have long hair
  • A subset of the dogs in set A and a subset of those in set B have the common properties of being black with short tails
  • A subset of the dogs in set A and a subset of those in set C have the common properties of being black with long hair.
  • A subset of the dogs in set B and a subset of those in set C have the common properties of having short tails and long hair.
  • A subset of the three subsets have the common properties of blackness, short tails and long hair.
 
(a)    Draw a relational (Venn) diagram that shows the interrelationships between the following concepts:
  • Solutions of an electrolyte
  • Solutions of a strong electrolyte
  • Solutions of a weak electrolyte
  • Solutions of a non-electrolyte
  • Concentrated solutions
  • Dilute solutions

You might, for example, begin with trying to portray diagrammatically that every aqueous solution is either (i) a solutions of an electrolyte, or (ii) a solution of a non-electrolyte.
 
(b)    Put each of the following solutions in the appropriate area of the diagram. That is, consider in which area of the diagram each solution “belongs”.
  • vodka (37% ethanol in water)
  • 300 g/L NaCl solution
  • 50% aqueous ethanoic acid solution
  • M sucrose solution
  • M copper sulfate (CuSO4) solution
  • 10 M HCl solution
  • M ammonia (NH3) solution
  • 18 M sulfuric acid (H2SO4) solution
  • M HCl solution
  • vinegar (5% ethanoic acid in water)
  • 5 M ammonia (NH3) solution
 
Remember that there is no single concentration that is a sharp dividing line between solutions that are classified as “concentrated” or “dilute”. Nevertheless, these terms are often used. Make practical decisions.
 

​


Answers
​

1.   A is a concentrated solution of a non-electrolyte solute.
      B is a dilute solution of a weak electrolyte solute.
      C is a dilute solution of a strong electrolyte solute.
      D is a dilute solution of a non-electrolyte solute.
      E is a concentrated solution of a weak electrolyte solute.
      F is a A concentrated solution of a strong electrolyte solute


2.
(a)     These are nonsense questions. Words describing strength (such as strong, weak, stronger, weaker, …..) are relevant to properties of solutes in solution, not of the solutions.
(b)        All of the following are valid statements about the solutions:
  •    A is a more concentrated solution (of sucrose) than both B and C.
  •    C is a more dilute (or, less concentrated) solution than both A and B.
  •    B is a more dilute solution than A, but is more concentrated than C
 

3.
(a)      All of the following are valid statements about the solutes:
  •    HX is a stronger (weak) electrolyte than either of HY or HZ.
  •    HZ is a weaker (weak) electrolyte than both HX and HY.
  •    HY is a weaker electrolyte than HX, but a stronger electrolyte than HZ.

(b)   The percentage of a weak electrolyte that ionises depends on the concentration of the solution. [The more dilute the solution, the more of the electrolyte ionises.] So the strengths of electrolytes can only be compared in solutions of the same concentration. (Although, in the example presented, the solutions would need to be of vastly different concentrations for the percentages ionised to be in a different order.]
 
​
4.     Nonsense. Misuse of terms.
​


5. Solution A is more  dilute … (that is less .. concentrated …) than solution B. Solution B is … more concentrated .. than solution C. The solute in solution A is a ... stronger .. electrolyte than the solute in solution B. In fact, because all of the HCl molecules ionize in solution, hydrochloric acid is a …. strong electrolyte …. . The solute in solution B is a …. weak electrolyte ...  because only some of the molecules ... ionise … . in solution,  but it is a … stronger electrolyte … than the solute in solution C. In solution C, none of the sucrose molecules ionise, so sucrose is called a … non-electrolyte .. .
 


​6. There are many possible ways to represent the relationships among these categories of solution. One way is shown. The various solutions have been placed in their appropriate areas.
​
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There is usually more than one way of diagrammatically representing relationships. No matter how the relational diagram is constructed, it should show:
  • Of all the aqueous solutions of substances, some are solutions of non-electrolytes, and some are solutions of electrolytes.
  • Of the aqueous solutions of electrolytes, some are solutions of strong electrolytes, and some are solutions of weak electrolytes.
  • Regardless of whether the solute is a strong electrolyte, a weak electrolyte, or a non-electrolyte, solutions may be either concentrated or dilute.
 
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1 Comment
Cameron N link
14/10/2021 16:10:16

Hello mate ggreat blog post

Reply



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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 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?
    • 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
    • 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