In [1]:

    

import math


    

In [3]:

    

class Reactant(object):
    
    def __init__(self, formula=None, molwt=None, mass=None, state=None, electrolyte=None, density=None, pk=None):
        self.formula = formula
        self.molwt = molwt
        self.mass = mass
        self.state = state
        self.electrolyte = electrolyte
        self.density = density
        self.pk = pk


    

In [25]:

    

def ph(reactants):
    '''
    lst of object having following attributes:
        * formula
        * molwt
        * state
        * electrolyte
        * density
        * pk
    '''

    volume    = 0.0
    C_Hplus   = 0.0
    C_OHminus = 0.0

    for reac in reactants:
        if reac.state == "solid" or reac.state == "gel" or reac.formula == "H2O":
            volume += reac.mass/reac.density/1000.0
    print "Volume = ", volume
    
    for reac in reactants:
        if reac.pk >  10.0:      # strong electrolyte
            if reac.electrolyte == "acid":
                C_Hplus += reac.mass/reac.molwt/volume
            elif reac.electrolyte == "base":
                C_OHminus += reac.mass/reac.molwt/volume
        else:                   # weak electrolyte
            if reac.electrolyte == "acid":
                C_Hplus += math.sqrt(math.exp(-1.0*reac.pk)*reac.mass/reac.molwt/volume)
            elif reac.electrolyte == "base":
                C_OHminus += math.sqrt(math.exp(-1.0*reac.pk)*reac.mass/reac.molwt/volume)

    if C_Hplus > C_OHminus:
        pH = -1.0*math.log(C_Hplus - C_OHminus, 10)
    else:
        pOH = -1.0*math.log(C_OHminus - C_Hplus, 10)
        pH = 14.0 - pOH
    return pH


    

In [27]:

    

naoh = Reactant(formula="NaOH", molwt=40.00, mass=40.0, state="solid", electrolyte="base", density=2.13, pk=10)
koh = Reactant(formula="KOH", molwt=56.11, mass=10.0, state="solid", electrolyte="base", density=2.044, pk=10)
h2o = Reactant(formula="H2O", molwt=18.02, mass=9970.0, state="liquid", electrolyte="neutral", density=0.9970, pk=10)

reactants = [naoh, h2o]


    

In [24]:

    

print "pH = {0:8.4f}".format(ph(reactants))


    

    




Volume =  10.0187793427
pH =  12.9992

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