aqueous-chemistry-electrochem

Aqueous Chemistry And Electrochemistry

Tutor skill for water chemistry, acid-base systems, redox, and electrochemical calculations. Useful for produced-water treatment, corrosion reasoning, and core chemical engineering coursework.

---

Module 1 - pH, pOH, And Buffers

def ph_from_h(h_mol_L):
    """pH from hydrogen ion concentration."""
    import math
    if h_mol_L <= 0:
        return None
    return -math.log10(h_mol_L)

def poh_from_oh(oh_mol_L):
    """pOH from hydroxide concentration."""
    import math
    if oh_mol_L <= 0:
        return None
    return -math.log10(oh_mol_L)

def henderson_hasselbalch(pka, acid_conc, base_conc):
    """Buffer relation for conjugate acid/base pair."""
    import math
    if acid_conc <= 0 or base_conc <= 0:
        return None
    return pka + math.log10(base_conc / acid_conc)

---

Module 2 - Alkalinity, Hardness, And Ionic Strength

def mgL_as_caco3(concentration_mgL, equivalent_weight):
    """
    Convert mg/L of species to mg/L as CaCO3.
    """
    if equivalent_weight <= 0:
        return None
    return concentration_mgL * 50.0 / equivalent_weight

def ionic_strength(concentrations_mol_L, charges):
    """
    I = 0.5 * sum(c_i * z_i^2)
    """
    if len(concentrations_mol_L) != len(charges):
        return None
    return 0.5 * sum(c * z**2 for c, z in zip(concentrations_mol_L, charges))

Common equivalent weights

Species	Eq. wt.
Ca2+	20.04
Mg2+	12.15
HCO3-	61.0
CO3 2-	30.0

---

Module 3 - Redox And Electrochemistry

def nernst_potential(E0_V, n_electrons, oxidized_activity, reduced_activity,
                     temperature_K=298.15):
    """
    Nernst equation:
    E = E0 - (RT/nF) ln(Q)
    For Ox + ne- -> Red, Q = a_red / a_ox
    """
    import math
    R = 8.314
    F = 96485.0
    if n_electrons <= 0 or oxidized_activity <= 0 or reduced_activity <= 0:
        return None
    q = reduced_activity / oxidized_activity
    return E0_V - (R * temperature_K / (n_electrons * F)) * math.log(q)

def faraday_mass_deposited(current_A, time_s, molar_mass_g_mol,
                           n_electrons, efficiency=1.0):
    """
    Faraday's law:
    m = I t M eta / (n F)
    """
    F = 96485.0
    if n_electrons <= 0:
        return None
    return current_A * time_s * molar_mass_g_mol * efficiency / (n_electrons * F)

---

Module 4 - Screening Logic

Problem	What to compute first
Buffer or titration question	Henderson-Hasselbalch or charge balance
Scaling or precipitation screen	pH, alkalinity, hardness, ionic strength
Electrolysis / plating	Faraday law
Corrosion-cell potential	Nernst equation and half-reaction direction
Produced-water treatment chemistry	Speciation basis, ionic strength, and CaCO3 conversion

---

Output Format

When using this skill, structure the answer as:

1. Species and reaction basis
2. Assumptions about equilibrium or ideality
3. Equation setup
4. Numerical result
5. Interpretation in physical or process terms

---

Learning Resources

Resource	Notes
Sawyer, McCarty, Parkin	Water chemistry / treatment classic
Bard and Faulkner	Electrochemistry reference
OpenStax Chemistry	Good acid-base and electrochem refreshers