Strong Acid

breed [ waters water ]          ;; water molecules
breed [ hydroxides hydroxide ]  ;; base molecules
breed [ hydroniums hydronium ]  ;; acid molecules

globals [
  pH
  base-added    ;; use to keep track of how much total base has been added
]

to setup
  clear-all
  set-default-shape waters "molecule2"
  set-default-shape hydroniums "molecule3"
  set-default-shape hydroxides "molecule1"
  create-waters 100           ;; creates constant volume of water in which to dilute acid
    [ set color blue ]
  create-hydroniums vol-acid  ;; creates VOL-ACID of hydronium ions
    [ set color green ]
  ask turtles                       ;; randomize position and heading of turtles
    [ setxy random-xcor random-ycor ]
  set base-added 0
  calculate-pH
  reset-ticks
  update-plots
end 

to go
  ask hydroxides [ react ]
  ask turtles
    [ fd 1                                        ;; move turtles around randomly
      rt random 10
      lt random 10 ]    ;; around the world
  tick
  calculate-pH
end 

;; adds hydroxide molecules to the solution

to add-base
  create-hydroxides vol-base
    [ set color red
      fd 1 ]
  set base-added base-added + vol-base
end 

;; hydroxide procedure

to react
  let partner one-of hydroniums-here   ;; see if there are any hydroniums here
  if partner != nobody                 ;; if one is found
    [ set breed waters                 ;; become water
      set color blue
      ask partner
        [ set breed waters             ;; partner becomes water too
          set color blue ] ]
end 

;; calculates the pH from the amount of the various ions in solution;
;; note that for simplicity the calculations don't take the true molar
;; concentration of water into account, but instead use an arbitrarily
;; chosen factor of 1000 to produce numbers lying in a reasonable range

to calculate-pH
  let volume count turtles
  let concH (count hydroniums / volume)
  let concOH (count hydroxides / volume)
  ifelse (concH = concOH)
    [ set pH 7 ]
    [ ifelse (concH > concOH)
      [ set pH (- log (concH / 1000) 10) ]
      [ let pOH (- log (concOH / 1000) 10)
        set pH 14 - pOH ] ]
end 

;; plotting procedures

to record-pH
  set-current-plot "Titration Curve"
  plotxy base-added pH
end 


; Copyright 2001 Uri Wilensky.
; See Info tab for full copyright and license.