@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
@prefix owl: <http://www.w3.org/2002/07/owl#> .
@prefix dcterms: <http://purl.org/dc/terms/> .
@prefix prefix: <http://qudt.org/vocab/prefix/> .
@prefix prov: <http://www.w3.org/ns/prov#> .
@prefix qkdv: <http://qudt.org/vocab/dimensionvector/> .
@prefix quantitykind: <http://qudt.org/vocab/quantitykind/> .
@prefix qudt: <http://qudt.org/schema/qudt/> .
@prefix si-unit: <https://si-digital-framework.org/SI/units/> .
@prefix skos: <http://www.w3.org/2004/02/skos/core#> .
@prefix sou: <http://qudt.org/vocab/sou/> .
@prefix unit: <http://qudt.org/vocab/unit/> .
@prefix vaem: <http://www.linkedmodel.org/schema/vaem#> .
@prefix voag: <http://voag.linkedmodel.org/schema/voag#> .

unit:PH
  a qudt:Unit ;
  dcterms:description """
  In chemistry the unit $\\textit{pH}$, also referred to as $\\textit{acidity}$ or $\\textit{basicity}$,
   is the negative logarithm (base 10) of the concentration of free protons (or hydronium ions).
  The definition of $pH$ in terms of hydrogen ions in solution is:

  $$\\text{pH}=-\\log_{10}(a_{H^+})\\equiv-\\log_{10}\\left(\\left[H^+\\right]\\right)$$

  Where $a_{H^+}$ is the equilibrium molar concentration of $H^+$ in the solution, the activity of
   the hydrogen ion in the solution.
  $$$$
  This definition is appropriate for concentrations equal to, or less than $1\\ mol/l$,
   where $aH+ \\equiv [H+]$, that is, $1\\ mol/L\\ HCl$ has a $pH$ of zero.
  $$$$
  To relate this to standard molality ($b^\\circ$), typically taken as $1 \\ mol/kg$,
   consideration is given to the activity ($a_{H^+}$) of the hydrogen ions.
  $$$$
  The activity can be expressed as:

  $$a_{H^+} = \\gamma_{H^+} \\times m_{H^+}$$

  Where, $\\gamma_{H^+}$ is the activity coefficient, which adjusts the molality to account for
   non-ideal behavior due to interactions between ions in the solution.
  $m_{H^+}$ is the molality of hydrogen ions in the solution relative to the standard molality,
   expressed in $mol/kg$.
  $$$$
  The expansion of $pH$ then becomes:

  $$\\text{pH} = -log_{10}\\left(m_{H+}\\times\\gamma_{H^+}\\right)$$

  $$$$
  This definition is relevant in more concentrated solutions or when precise thermodynamic calculations are required.
  It reflects how the properties of the solution deviate from ideal behavior and provides a more accurate understanding of the $pH$ under various conditions.
  $$$$
  While $pH$ is a universally recognized scale for expressing hydrogen ion activity,
  its appropriateness and accuracy can diminish under conditions of extremely high
  ionic strength, non-aqueous environments, high temperatures, or very high or low $pH$ values.
  In such cases, alternative measurement strategies might be required to obtain meaningful and accurate descriptions of acidity or basicity.
  """^^qudt:LatexString ;
  qudt:applicableSystem sou:ASU ;
  qudt:applicableSystem sou:CGS ;
  qudt:applicableSystem sou:CGS-EMU ;
  qudt:applicableSystem sou:CGS-ESU ;
  qudt:applicableSystem sou:CGS-GAUSS ;
  qudt:applicableSystem sou:IMPERIAL ;
  qudt:applicableSystem sou:PLANCK ;
  qudt:applicableSystem sou:SI ;
  qudt:conversionMultiplier 0.0 ;
  qudt:conversionMultiplierSN 0.0E0 ;
  qudt:hasDimensionVector qkdv:A0E0L0I0M0H0T0D1 ;
  qudt:hasQuantityKind quantitykind:Acidity ;
  qudt:hasQuantityKind quantitykind:Basicity ;
  qudt:informativeReference "https://iupac.org/wp-content/uploads/2019/05/IUPAC-GB3-2012-2ndPrinting-PDFsearchable.pdf"^^xsd:anyURI ;
  qudt:symbol "pH" ;
  qudt:ucumCode "[pH]"^^qudt:UCUMcs ;
  rdfs:comment "Unsure about dimensionality of pH; conversion requires a log function not just a multiplier"@en ;
  rdfs:isDefinedBy <http://qudt.org/3.2.1/vocab/unit> ;
  rdfs:label "Acidity" ;
  rdfs:label "Acidity"@en .