Buffer Titration

Buffer Titration preview image

1 collaborator

Screen_shot_2018-02-02_at_12.53.50_pm lin xiang (Author)

Tags

acid and base 

Tagged by lin xiang 18 days ago

buffer 

Tagged by lin xiang 18 days ago

chemistry 

Tagged by lin xiang 18 days ago

titration 

Tagged by lin xiang 18 days ago

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WHAT IS IT?

How does a buffer behave differently from a strong acid or a strong base during titration? Check this model. Starting at the same pH level, see how much more titrant is needed to cause a significant pH change.

HOW IT WORKS

  • A strong acid and an acid buffer are compared side by side. They both start at a ph of 3 and are titrated by NaOH. Ka = 1.8E-5

  • A strong base and an alkaline buffer are compared side by side. They both start at a ph of 11 and are titrated by HCl. Kb = 1.8E-5

  • The starting pHs are 3 for acidic solutions and 11 for basic solutions. We do not let users set up a random starting pH because every buffer has a particular buffer zone.

HOW TO USE IT

  1. Choose a test, and then determine the titrant concentration and dose.
  2. Run the model to titrate.

Note: -Don't change the titrant's concentration and dose during titration. -Use switches to hide some molecules or ions to help observations.

THINGS TO NOTICE

  • Dissociation of the strong acid/base and weak acid/base.
  • The pH changes in the titration processes of the strong acid/base and buffer.

RELATED MODELS

See more chemistry models at https://sites.google.com/view/3d-science-abm/physics-chemistry

CREDITS AND REFERENCES

Dr. Lin Xiang created this module at the University of Kentucky in 2022. If you mention this model in a publication, we ask that you include the citations below.

Xiang, L. (2022). Buffer Titration. Department of STEM Education, University of Kentucky, Lexington, KY.

CC BY-NC-SA 4.0

This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 License. To view a copy of this license, visit https://creativecommons.org/licenses/by-nc-sa/4.0/.

Comments and Questions

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Click to Run Model

breed [HAs HA]
breed [A-s A-]
breed [Bs B]
breed [BHs BH]
breed [H3OS H30]
breed [OHs OH]
breed [legends legend]

turtles-own[ ]
globals [Starting-pH
  kb ka
  Num-H-l Num-H-r
  Num-OH-l Num-OH-r
  num-B-l num-B-r
  num-BH-l num-BH-r
  num-HA-l num-HA-r
  num-A-l num-A-r
  vol-1-l vol-1-r
  vol-titrant-l vol-titrant-r
  current-conc-H-l current-conc-H-r
  current-conc-OH-l current-conc-OH-r
  current-conc-B-l current-conc-B-r
  current-conc-BH-l current-conc-BH-r
  current-conc-A-l current-conc-A-r
  current-conc-HA-l current-conc-HA-r
  current-ph-l current-ph-r
  current-pOH-l current-pOH-r
  M-H-l M-H-r
  M-T-l M-T-r
  M-OH-l M-OH-r
  M-BH-l M-BH-r
  M-B-l M-B-r
  M-B-1-l M-B-1-r
  M-HA-l M-HA-r
  M-HA-1-l M-HA-1-r
  M-A-l M-A-r
  unit-num-b
  unit-num-ha
]



;;;;;;;;;;;;;;;;;;;;;;;;;
;;                     ;;
;;  Setup procedures   ;;
;;                     ;;
;;;;;;;;;;;;;;;;;;;;;;;;;

to setup
  (ifelse
    Choose-a-test = "Strong Acid and Acidic Buffer"
    [ ca
      set-shapes
      set-bk
      set Starting-pH 3
      set-legends-a
      set-HCl
      set-acetic-acid]


    Choose-a-test = "Strong Base and Alkaline Buffer"
      [ca
       set-shapes
       set-bk
       set Starting-pH 11
       set-legends-b
       set-NaOH
        set-NH3])

  reset-ticks
end 

to set-shapes
  set-default-shape ohs "ab-oh-1"
  set-default-shape h3os "ab-h3o-1"
  set-default-shape has "ab-ha-1"
  set-default-shape a-s "ab-ha-2"
  set-default-shape bs "ab-b-1"
  set-default-shape bhs "ab-b-2"
end 

to set-bk
  ask patches [set pcolor 91.5 + random-float 0.5]
  ask patches with [ pycor >= max-pycor - 1 or pycor < 3] [set pcolor 101]
  ask patches with [ pxcor = max-pxcor or pxcor = min-pxcor] [set pcolor 101]
  ask patches with [ pxcor = 33 or pxcor = 34 or pxcor = 35] [set pcolor 101]
end 

to set-tt-properties-l
   set size 1.25
   setxy 1 + random-float 31 4 + random-float (max-pycor - 7)
end 

to set-tt-properties-r
   set size 1.25
   setxy 36 + random-float 31 4 + random-float (max-pycor - 7)
end 

to set-legends-a
  create-legends 10

 ask legend 0
  [set shape "ab-h3o-1"
    set size 1.75
    setxy 12.5 1]

  ask legend 1
  [set shape "blank"
    set size 1.5
    set label "Hydronium (H3O+)"
    set label-color white
    setxy 22 1.3]

  ask legend 2
   [set shape "ab-OH-1"
    set size 1.75
    set color 85
    setxy 25 1]

  ask legend 3
  [set shape "blank"
    set size 1.5
    set label "Hydroxide (OH-)"
    set label-color white
    setxy 33 1.3]

  ask legend 4
   [set shape "ab-ha-1"
    set size 1.75
    set color 116.5
    setxy 36.5 1]

  ask legend 5
  [set shape "blank"
    set size 1.5
    set label "Acid molecule"
    set label-color white
    setxy 43.8 1.3]

  ask legend 6
   [set shape "ab-ha-2"
    set size 1.75
    set color 113.5
    setxy 47.5 1]

  ask legend 7
  [set shape "blank"
    set size 1.5
    set label "Conjugate base"
    set label-color white
    setxy 55.5 1.3]

  ask legend 8
  [set shape "blank"
    set size 3
    set label "Hydrocloric Acid (HCl)"
    set label-color white
    setxy 19.5 36.5]

  ask legend 9
  [set shape "blank"
    set size 3
    set label "Acetic acid/Acetate Buffer (CH3COOH/CH3COO-)"
    set label-color white
    setxy 62 36.5]
end 

to set-legends-b
  create-legends 10

 ask legend 0
  [set shape "ab-h3o-1"
    set size 1.75
    setxy 13.5 1]

  ask legend 1
  [set shape "blank"
    set size 1.5
    set label "Hydronium (H3O+)"
    set label-color white
    setxy 22 1.3]

  ask legend 2
   [set shape "ab-OH-1"
    set size 1.75
    set color 85
    setxy 25.5 1]

  ask legend 3
  [set shape "blank"
    set size 1.5
    set label "Hydroxide (OH-)"
    set label-color white
    setxy 33 1.3]

  ask legend 4
   [set shape "ab-b-1"
    set size 1.75
    set color 42.5
    setxy 36.5 1]

  ask legend 5
  [set shape "blank"
    set size 1.5
    set label "Base molecule"
    set label-color white
    setxy 43.5 1.3]

  ask legend 6
   [set shape "ab-b-2"
    set size 1.75
    set color 62.5
    setxy 47.5 1]

  ask legend 7
  [set shape "blank"
    set size 1.5
    set label "Conjugate acid"
    set label-color white
    setxy 55 1.3]

  ask legend 8
  [set shape "blank"
    set size 3
    set label "Sodium Hydroxide (NaOH)"
    set label-color white
    setxy 20 36.5]

  ask legend 9
  [set shape "blank"
    set size 3
    set label "Ammonia-Ammonium Chloride Buffer (NH3/NH4+)"
    set label-color white
    setxy 62 36.5]
end 

to set-HCl

  set vol-1-l 100
  set vol-titrant-l 0
  set current-conc-H-l 10 ^ (- Starting-pH)                  ;starting ph of hcl is 3.5
  set current-ph-l Starting-pH
  set M-H-l current-conc-H-l * vol-1-l * 0.001          ;determine the mole of H+
  set M-A-l M-H-l
  set M-HA-l M-H-l
  set current-conc-A-l (M-A-l / (vol-1-l * 0.001))  ;determine initial HA concentration
  set current-conc-HA-l 0                       ;there is no HA
  set current-Conc-OH-l 10 ^ (-14) / current-conc-H-l          ;calculate the concentration of OH-
  set M-OH-l current-Conc-OH-l * vol-1-l * 0.001                 ;calculate exisitng mole of OH-



  set num-H-l round (1000 * (1.3895 ^ (-1 * current-ph-l)))     ;find the amount of visual H+
  set num-OH-l round (10000 / (num-H-l))                        ;find the amount of visual OH-

  if Hide-acid-molecule-and-conjugate-base? = false
   [create-a-s num-H-l [set-tt-properties-l set size 1.25 set color 113.5]]

  if Hide-hydronium-and-hydroxide? = false
  [set num-H-l round (1000 * (1.3895 ^ (-1 * current-ph-l)))     ;find the amount of visual H+
   set num-OH-l round (10000 / (num-H-l))                        ;find the amount of visual OH-
   create-h3os num-H-l [set-tt-properties-l set size 1.25 ]
   create-ohs num-OH-l [set-tt-properties-l set size 1.25 set color 85]]
end 

to set-acetic-acid
  set ka 1.8 * (10 ^ -5)
  set vol-1-r 100
  set vol-titrant-r 0
  set current-conc-H-r 10 ^ (- Starting-pH)
  set current-ph-r Starting-pH
  set current-conc-HA-r (current-conc-H-r * (current-conc-H-r + ka) / ka)  ;determine initial HA concentration
  set current-conc-A-r current-conc-H-r                                   ;determine initial HA concentration
  set M-HA-r current-conc-HA-r * vol-1-r * 0.001   ;determine the mole of HA
  set M-H-r current-conc-H-r * vol-1-r * 0.001     ;determine the mole of H+
  set M-A-r M-H-r


  if Hide-acid-molecule-and-conjugate-base? = false
  [ set num-HA-r round (2500 * sqrt (sqrt (M-HA-r)))
    set num-A-r round (100 * sqrt (sqrt (M-A-r)))
    create-has num-HA-r [set-tt-properties-r set size 1.25 set color 116.5]
    create-a-s num-A-r [set-tt-properties-r set size 1.25 set color 113.5]
    set unit-num-ha (M-HA-r / num-ha-r) ]

  if Hide-hydronium-and-hydroxide? = false
  [set num-H-r round (1000 * (1.3895 ^ (-1 * current-ph-r)))     ;find the amount of visual H+
   set num-OH-r round (10000 / (num-H-r))                        ;find the amount of visual OH-
   create-h3os num-H-r [set-tt-properties-r set size 1.25 ]
   create-ohs num-OH-r [set-tt-properties-r set size 1.25 set color 85]]
end 

to set-NaOH

  set vol-1-l 100
  set vol-titrant-l 0
  set current-conc-OH-l 10 ^ (- (14 - Starting-pH))
  set current-ph-l Starting-pH
  set M-OH-l current-conc-OH-l * vol-1-l * 0.001   ;determine the mole of hydroxide
  set M-B-l M-OH-l
  set M-BH-l M-OH-l
  set current-conc-BH-l (M-BH-l / (vol-1-l * 0.001))  ;determine initial conjugate acid concentration
  set current-conc-B-l 0                       ;there is no base molecule
  set current-Conc-H-l 10 ^ (-14) / current-conc-OH-l          ;calculate the concentration of H+
  set M-H-l current-Conc-H-l * vol-1-l * 0.001                 ;calculate exisitng mole of H+

  set num-H-l round (1000 * (1.3895 ^ (-1 * current-ph-l)))     ;find the amount of visual H+
  set num-OH-l round (10000 / (num-H-l))                        ;find the amount of visual OH-

  if Hide-base-molecule-and-conjugate-acid? = false
   [create-BHs num-OH-l [set-tt-properties-l set size 1.25 set color 62]]

  if Hide-hydronium-and-hydroxide? = false
  [set num-H-l round (1000 * (1.3895 ^ (-1 * current-ph-l)))     ;find the amount of visual H+
   set num-OH-l round (10000 / (num-H-l))                        ;find the amount of visual OH-
   create-h3os num-H-l [set-tt-properties-l set size 1.25 ]
   create-ohs num-OH-l [set-tt-properties-l set size 1.25 set color 85]]
end 

to set-NH3

  set kb 1.8 * (10 ^ -5)
  set vol-1-r 100
  set vol-titrant-r 0
  set current-conc-OH-r 10 ^ (- (14 - Starting-pH))
  set current-ph-r Starting-pH
  set current-conc-B-r (current-conc-OH-r * (current-conc-OH-r - kb) / kb)  ;determine initial Base concentration
  set current-conc-BH-r current-conc-OH-r  ;determine initial conjugate acid concentration
  set M-B-r current-conc-B-r * vol-1-r * 0.001   ;determine the mole of base
  set M-OH-r current-conc-OH-r * vol-1-r * 0.001   ;determine the mole of OH-
  set M-BH-r M-OH-r

  if Hide-base-molecule-and-conjugate-acid? = false
  [set num-B-r round (2500 * sqrt (sqrt (M-B-r)))
   set num-BH-r round (100 * sqrt (sqrt (M-BH-r)))
   create-Bs num-B-r [set-tt-properties-r set size 1.25 set color 42]
   create-BHs num-BH-r[set-tt-properties-r set size 1.25 set color 62]
   set unit-num-b (M-b-r / num-b-r)]

  if Hide-hydronium-and-hydroxide? = false
  [set num-H-r round (1000 * (1.3895 ^ (-1 * current-ph-r)))     ;find the amount of visual H+
   set num-OH-r round (10000 / (num-H-r))                        ;find the amount of visual OH-
   create-h3os num-H-r [set-tt-properties-r set size 1.25 ]
   create-ohs num-OH-r [set-tt-properties-r set size 1.25 set color 85]]
end 


;;;;;;;;;;;;;;;;;;;;;;;;;
;;                     ;;
;;  GO procedures      ;;
;;                     ;;
;;;;;;;;;;;;;;;;;;;;;;;;;

to go
  move

 (ifelse
    Choose-a-test = "Strong Acid and Acidic Buffer"
     [if current-conc-BH-r != 0 [setup]

      titration-HCl
      titration-acetic-acid

      (ifelse
        Hide-acid-molecule-and-conjugate-base? = true and count a-s > 0
         [if any? a-s [ask a-s [die]] if any? has [ask has [die]]]
        Hide-acid-molecule-and-conjugate-base? = false and count a-s > 0
         [dissociation-a]
        Hide-acid-molecule-and-conjugate-base? = false and count a-s <= 0
         [ ;right box
            set M-HA-1-r (current-conc-HA-r * vol-1-r * 0.001)
            let num-HA-to-be round (M-HA-1-r / unit-num-ha)
            create-has num-HA-to-be [set-tt-properties-r set size 1.25 set color 116.5]
            create-a-s (num-HA-r - num-HA-to-be + num-A-r)[set-tt-properties-r set size 1.25 set color 113.5]

           ; left box
            create-a-s round (1000 * (1.3895 ^ ( - Starting-pH))) [set-tt-properties-l set size 1.25 set color 113.5]])

   (ifelse
    Hide-hydronium-and-hydroxide? = true and count OHs > 0
    [ask h3os [die] ask ohs [die]]
    Hide-hydronium-and-hydroxide? = false and count ohs > 0
    [acid-base-equilibrium]
    Hide-hydronium-and-hydroxide? = false and count ohs <= 0
    [;left box
     set num-H-l round (1000 * (1.3895 ^ (-1 * current-pH-l)))
     set num-OH-l round (10000 / (num-H-l))
     create-h3os num-H-l [set-tt-properties-l set size 1.25 ]
     create-ohs num-OH-l [set-tt-properties-l set size 1.25 set color 85]

     ;right box
     set num-H-r round (1000 * (1.3895 ^ (-1 * current-pH-r)))
     set num-OH-r round (10000 / (num-H-r))
     create-h3os num-H-r [set-tt-properties-r set size 1.25 ]
     create-ohs num-OH-r [set-tt-properties-r set size 1.25 set color 85]
    ])

     if (vol-titrant-l + vol-titrant-r) / 2  >= (Total-mL-of-titrant-added - 0.05) [user-message "Have added the specified amount of titrant." stop]
    ]

    Choose-a-test = "Strong Base and Alkaline Buffer"
    [ if current-conc-A-r != 0 [setup]

      titration-NaOH
      titration-NH3

  (ifelse
    Hide-base-molecule-and-conjugate-acid? = true and count BHs > 0
      [if any? BHs [ask BHs [die]] if any? Bs [ask Bs [die]]]
    Hide-base-molecule-and-conjugate-acid? = false and count BHs > 0
      [dissociation-b]
    Hide-base-molecule-and-conjugate-acid? = false and count BHs <= 0
    [;right box
      set M-B-1-r (current-conc-B-r * vol-1-r * 0.001)
      let num-B-to-be round (M-B-1-r / unit-num-b)
      create-bs num-b-to-be [set-tt-properties-r set size 1.25 set color 42]
      create-BHs (num-b-r - num-b-to-be + num-BH-r)[set-tt-properties-r set size 1.25 set color 62]
      ;left box
       create-BHs round (1000 * (1.3895 ^ ( - Starting-pH))) [set-tt-properties-l set size 1.25 set color 62]])

   (ifelse
    Hide-hydronium-and-hydroxide? = true and count OHs > 0
      [ask h3os [die] ask ohs [die]]
    Hide-hydronium-and-hydroxide? = false and count ohs > 0
       [acid-base-equilibrium]
    Hide-hydronium-and-hydroxide? = false and count ohs <= 0
     [;left box
      set num-H-l round (1000 * (1.3895 ^ (-1 * current-pH-l)))
      set num-OH-l round (10000 / (num-H-l))
      create-h3os num-H-l [set-tt-properties-l set size 1.25 ]
      create-ohs num-OH-l [set-tt-properties-l set size 1.25 set color 85]

      ;right box
      set num-H-r round (1000 * (1.3895 ^ (-1 * current-pH-r)))
      set num-OH-r round (10000 / (num-H-r))
      create-h3os num-H-r [set-tt-properties-r set size 1.25 ]
      create-ohs num-OH-r [set-tt-properties-r set size 1.25 set color 85]])
     if (vol-titrant-l + vol-titrant-r) / 2  >= (Total-mL-of-titrant-added - 0.05) [user-message "Have added the specified amount of titrant." stop]
  ])

  tick
end 

to move
  ask turtles with [breed != legends]    ;ask non-legend turtles
  [rt random 360                            ;rotate
    if [pcolor] of patch-at dx dy <= 92 and [pcolor] of patch-at dx dy >= 91.5    ;if the patch-ahead has the proper color
      [fd 0.5                                                                       ;move forward
       if ycor < 4 [set ycor 4]                                                   ;if ycor is low, put ycor higher
  ]]
end 

to acid-base-equilibrium

  ;left box
  set num-H-l round (1000 * (1.3895 ^ (-1 * current-pH-l)))
  set num-OH-l round (10000 / (num-H-l))

  let current-H-l count H3Os with [xcor < 33]
  let current-OH-l count OHs with [xcor < 33]

  (ifelse
    (num-H-l) > current-H-l
     [create-h3os abs ((num-H-l) - current-H-l) [set-tt-properties-l set size 1.25]]
    (num-H-l) < current-H-l
    [ask n-of abs ((num-H-l) - current-H-l) h3os with [xcor < 33][die]])

   (ifelse
    (num-OH-l) > current-OH-l
    [create-ohs abs ((num-OH-l) - current-OH-l) [set-tt-properties-l set size 1.25 set color 85]]
    (num-OH-l) < current-OH-l
    [ask n-of abs ((num-OH-l) - current-OH-l) OHs with [xcor < 33] [die]])

  ;right box
   set num-H-r round (1000 * (1.3895 ^ (-1 * current-pH-r)))
   set num-OH-r round (10000 / (num-H-r))

  let current-H-r count H3Os with [xcor > 35]
  let current-OH-r count OHs with [xcor > 35]

  (ifelse
    (num-H-r) > current-H-r
     [create-h3os abs ((num-H-r) - current-H-r) [set-tt-properties-r set size 1.25]]
    (num-H-r) < current-H-r
    [ask n-of abs ((num-H-r) - current-H-r) h3os with [xcor > 35][die]])

   (ifelse
    (num-OH-r) > current-OH-r
    [create-ohs abs ((num-OH-r) - current-OH-r) [set-tt-properties-r set size 1.25 set color 85]]
    (num-OH-r) < current-OH-r
    [ask n-of abs ((num-OH-r) - current-OH-r) OHs with [xcor > 35] [die]])
end 

to dissociation-b
  set M-B-1-r (current-conc-b-r * vol-1-r * 0.001)
  let num-b-to-be round (M-b-1-r / unit-num-b)
  let current-num-b count bs with [xcor > 35]

  if current-num-b > num-b-to-be
   [if any? bs with [xcor > 35]
      [ask up-to-n-of (current-num-b - num-b-to-be) bs with [xcor > 35] [set breed bhs set color 62]]]

  let T-of-tick Titrant-concentration * 0.001 * Titrant-dose   ;calculate the added mole of H+ in this tick
  if M-B-r - M-T-r <= -0.5 * t-of-tick
    [if any? bs with [xcor > 35] [ask bs with [xcor > 35] [set breed bhs set color 62]]]
end 

to dissociation-a

  set M-HA-1-r (current-conc-HA-r * vol-1-r * 0.001)
  let num-HA-to-be round (M-HA-1-r / unit-num-ha)
  let current-num-ha count has with [xcor > 35]

  if current-num-ha > num-HA-to-be
   [if any? Has with [xcor > 35]
      [ask up-to-n-of (current-num-ha - num-HA-to-be) has with [xcor > 35] [set breed a-s set color 113]]]

  let T-of-tick Titrant-concentration * 0.001 * Titrant-dose   ;calculate the added mole of OH- in this tick
  if M-HA-r - M-T-r <= -0.5 * t-of-tick
    [if any? Has with [xcor > 35] [ask has with [xcor > 35] [set breed a-s set color 113]]]
end 

to titration-NaOH
     set current-Conc-H-l 10 ^ (-14) / current-conc-OH-l      ;calculate the concentration of H+
     set M-H-l current-Conc-H-l * (vol-1-l) * 0.001             ;calculate exisitng mole of H+
     set vol-titrant-l vol-titrant-l + Titrant-dose               ;increase Titrant volume
     set vol-1-l vol-1-l + Titrant-dose                           ;increase total volume
     let T-of-tick Titrant-concentration * 0.001 * Titrant-dose   ;calculate the added mole of H+ in this tick
     set M-T-l (M-T-l + t-of-tick)                                ;update total mole of titant

    (ifelse
       current-conc-OH-l >= 10 ^ (-7)                         ;if base + acid
        [(ifelse
          M-B-l > M-T-l                                          ;if more OH- than H+
          [set current-conc-OH-l (M-B-l - M-T-l) / (vol-1-l * 0.001)              ;calculate the concentration of OH-
           ifelse current-conc-OH-l > 10 ^ (-6)
            [set current-ph-l (14 - (- log current-conc-OH-l 10))]                   ;calculate the ph
            [set current-conc-OH-l (10 ^ (-7) + current-conc-OH-l)          ;consider water self-ionizaiton
             set current-ph-l (14 - (- log current-conc-OH-l 10))]]                 ; find current pH

          M-B-l < M-T-l
          [set M-H-l (M-T-l - M-B-l)                              ;if more H+ than OH-,calculate left mole of H+
           set current-conc-H-l M-H-l / (vol-1-l * 0.001)             ;calculate the concentration of OH-
           ifelse current-conc-H-l > 10 ^ (-6)
            [set current-ph-l (- log current-conc-H-l 10)]       ;calculate the concentration of H+
            [set current-conc-H-l ((10 ^ (-7) + current-conc-H-l))  ;consider water self-ionizaiton
             set current-ph-l (- log current-conc-H-l 10)]]         ;calculate the concentration of H+

          M-B-l = M-T-l
          [set current-conc-H-l 10 ^ (-7) set current-ph-l (- log current-conc-H-l 10)])
        ]

       current-conc-OH-l < 10 ^ (-7)                                 ;if acid + acid
        [let total-H-l (M-H-l + T-of-tick)                                ;calculate the total mole of H+
         set current-conc-H-l total-H-l / (vol-1-l * 0.001)           ;calculate the concentration of OH-
        set current-ph-l (- log current-conc-H-l 10)])               ;Find ph
end 

to titration-NH3
     set vol-titrant-r vol-titrant-r + Titrant-dose               ;increase Titrant volume
     set vol-1-r vol-1-r + Titrant-dose                           ;increase total volume
     let T-of-tick Titrant-concentration * 0.001 * Titrant-dose                     ;calculate the added mole of OH- in this tick
     set M-T-r (M-T-r + t-of-tick)                                ;update total mole of titant


 (ifelse
      (M-B-r - M-T-r)  >= T-of-tick * 0.5                                     ;if more base (half tick mole) than H+, i.e., before the equivalent point
      [set current-conc-B-r (M-B-r - M-T-r) / (vol-1-r * 0.001)             ;update base concentration
       ifelse  ((M-BH-r + M-T-r) / (vol-1-r * 0.001)) -  (M-T-r / (vol-1-r * 0.001)) > 0.0008   ;update BH concentration. consider the initial BH concentration
        [set current-conc-BH-r ((M-BH-r + M-T-r) / (vol-1-r * 0.001))]
        [set current-conc-BH-r (M-T-r / (vol-1-r * 0.001))]
       set current-conc-OH-r (kb * current-conc-B-r / current-conc-BH-r)  ;find current OH- concentration
       set current-ph-r (14 - (- log current-conc-OH-r 10))]                 ; find current pH

      M-B-r - M-T-r < T-of-tick * 0.5  and  M-B-r - M-T-r > -0.5 * T-of-tick                    ;if at the equivalent point
      [set current-conc-BH-r (M-B-r / (vol-1-r * 0.001))                                ;update A- concentration
       let ka-r (10 ^ (-14) / kb)
       set current-conc-H-r (-0.5 * (ka-r - sqrt (ka-r * ka-r + 4 * ka-r * current-conc-BH-r)))  ;find H+ concentration using Ka
       set current-pH-r (- log current-conc-H-r 10)                                      ;find current ph using pH
       set current-conc-b-r current-conc-h-r]                                    ;update Base molecule concentration

      M-B-r - M-T-r <= -0.5 * T-of-tick                                          ; if after the equivalent point
      [set current-conc-b-r 0                                              ;update Base molecule concentration
       set current-conc-BH-r (M-B-r) / (vol-1-r * 0.001)                   ;update BH concentration
       set current-conc-H-r ((M-T-r - M-B-r) / (vol-1-r * 0.001))                ; find H+ concentration
       set current-ph-r (- log current-conc-H-r 10)])                        ;find current ph using pOH
end 

to titration-HCl
     set current-Conc-OH-l 10 ^ (-14) / current-conc-H-l          ;calculate the concentration of OH-
     set M-OH-l current-Conc-OH-l * (vol-1-l) * 0.001   ;calculate exisitng mole of OH-
     set vol-titrant-l vol-titrant-l + Titrant-dose               ;increase Titrant volume
     set vol-1-l vol-1-l + Titrant-dose                           ;increase total volume
     let T-of-tick Titrant-concentration * 0.001 * Titrant-dose   ;calculate the added mole of OH- in this tick
     set M-T-l (M-T-l + t-of-tick)                                ;update total mole of titant

    (ifelse
       current-conc-H-l >= 10 ^ (-7)                         ;if acid + base
        [(ifelse
          M-HA-l > M-T-l                                          ;if more H+ than OH-
          [set current-conc-H-l (M-HA-l - M-T-l) / (vol-1-l * 0.001)              ;calculate the concentration of H+
           set current-conc-A-l (M-HA-l / (vol-1-l * 0.001))
           ifelse current-conc-H-l > 10 ^ (-6)
            [set current-ph-l (- log current-conc-H-l 10)]                   ;calculate the ph
            [set current-conc-H-l (10 ^ (-7) + current-conc-H-l);consider water self-ionizaiton
             set current-ph-l (- log current-conc-H-l 10)]]                  ; find current pH


          M-HA-l < M-T-l
          [set M-OH-l (M-T-l - M-HA-l)                              ;if more OH- than H+,calculate left mole of OH-
           set current-conc-OH-l M-OH-l / (vol-1-l * 0.001)             ;calculate the concentration of OH-
           set current-conc-A-l (M-HA-l / (vol-1-l * 0.001))
           ifelse current-conc-OH-l > 10 ^ (-6)
            [set current-conc-H-l 10 ^ (-14) / current-conc-OH-l set current-ph-l (- log current-conc-H-l 10)]       ;calculate the concentration of H+
            [set current-conc-OH-l (10 ^ (-7) + current-conc-OH-l)           ;consider water self-ionizaiton
             set current-conc-H-l 10 ^ (-14) / current-conc-OH-l set current-ph-l (- log current-conc-H-l 10)]]         ;calculate the concentration of H+

          M-HA-l = M-T-l
          [set current-conc-A-l (M-HA-l / (vol-1-l * 0.001))
           set current-conc-H-l 10 ^ (-7) set current-ph-l (- log current-conc-H-l 10)])
           ]

       current-conc-H-l < 10 ^ (-7)                                 ;if base + base
        [set current-conc-A-l (M-HA-l / (vol-1-l * 0.001))
         let total-OH-l (M-OH-l + T-of-tick)                                ;calculate the total mole of OH-
         set current-conc-OH-l total-OH-l / (vol-1-l * 0.001)           ;calculate the concentration of OH-
         set current-conc-H-l 10 ^ (-14) / current-conc-OH-l           ;calculate the concentration of H+
         set current-ph-l (- log current-conc-H-l 10)])               ;Find ph
end 

to titration-acetic-acid
     set vol-titrant-r vol-titrant-r + Titrant-dose               ;increase Titrant volume
     set vol-1-r vol-1-r + Titrant-dose                           ;increase total volume
     let T-of-tick Titrant-concentration * 0.001 * Titrant-dose  ;calculate the added mole of OH- in this tick
     set M-T-r (M-T-r + t-of-tick)                                ;update total mole of titant


 (ifelse
      M-HA-r - M-T-r > 0.5 * t-of-tick                                             ;if more HA than OH-, i.e., before the equivalent point
      [set current-conc-HA-r (M-HA-r - M-t-r) / (vol-1-r * 0.001)             ;update HA concentration
      ifelse  ((M-A-r + M-T-r) / (vol-1-r * 0.001)) -  (M-T-r / (vol-1-r * 0.001)) > 0.0008     ;update A- concentration. consider the initial A concentration
         [set current-conc-A-r ((M-A-r + M-T-r) / (vol-1-r * 0.001))]
         [set current-conc-A-r (M-T-r / (vol-1-r * 0.001))]
       set current-conc-H-r (ka * current-conc-HA-r / current-conc-A-r)  ;find current H+ concentration
       set current-ph-r (- log current-conc-H-r 10)]                 ; find current pH

      M-HA-r - M-T-r <= 0.5 * t-of-tick and M-HA-r - M-T-r > -0.5 * t-of-tick                  ;if at the equivalent point
      [set current-conc-A-r (M-HA-r / (vol-1-r * 0.001))  ;update A- concentration
       let kb-r (10 ^ (-14) / ka)
       set current-conc-OH-r (-0.5 * (kb-r - sqrt (kb-r * kb-r + 4 * kb-r * current-conc-A-r))) ;find OH- concentration using Kb
       set current-pOH-r (- log current-conc-OH-r 10)            ;find current ph using pOH
       set current-ph-r (14 - current-pOH-r)            ;find current ph using pOH
       set current-conc-HA-r current-conc-OH-r]         ;update HA concentration


     M-HA-r - M-T-r <= -0.5 * t-of-tick                                   ; if after the equivalent point
      [set current-conc-HA-r 0                                          ;update HA concentration
       set current-conc-A-r (M-HA-r / (vol-1-r * 0.001))                    ;update A- concentration
       set current-conc-OH-r ((M-T-r - M-HA-r) / (vol-1-r * 0.001))           ; find OH- concentration
       set current-ph-r (14 - (- log current-conc-OH-r 10))])             ;find current ph using pOH
end 

There are 3 versions of this model.

Uploaded by When Description Download
lin xiang 19 days ago Minor adjustment Download this version
lin xiang 19 days ago Fix plotting bugs Download this version
lin xiang 19 days ago Initial upload Download this version

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