Precision Digital Conductivity Meter
Alternating-current impedance bridge operating at 1.0 kHz with auto-ranging conductance sensitivity from 0.01 μS to 200 mS and digital resolution of 0.001 mS.
Chemistry / Conductometric Acid Mixture Titration
FREE TO EXPLORELABORATORY 32 · NATURAL SCIENCES
Conductometric Titration of Strong and Weak Acid Mixtures
Determine the individual concentrations of hydrochloric acid (strong acid) and acetic acid (weak acid) in an unknown binary mixture by conductometric titration with standardized sodium hydroxide. Explore interactive analytical gravimetry, Class A volumetric glassware and density determination.
MEASURE · CALIBRATE · ANALYSE
Your virtual chemistry laboratory.
MEASURED ELECTROLYTIC CONDUCTANCE G_RAW—
MEASUREMENT STATUS
Ready to dispense 1.0 mL of liquid.
Adjust V(NaOH) V, then weigh the dispensed aliquot.
Mass observations are determined by the high-precision thermodynamic equation of state for pure liquid water. Readings reflect thermal equilibrium and analytical balance force restoration.
Physical chemistry assumptions and metrological limits
['Conductometric titration accuracy degrades at high ionic strengths (> 0.1 M) due to interionic Debye-Huckel-Onsager electrophoretic and relaxation effects, which cause slight non-linearity in the conductance branches.', 'The presence of high background concentrations of non-reactive inert salts (e.g., 1 M NaNO₃ or K₂SO₄) elevates total solution conductance to high baseline levels, reducing relative signal-to-noise sensitivity for the titration inflection points.', 'Near the equivalence point of very weak acids (pK_a > 7) or very dilute solutions (< 10⁻³ M), hydrolysis of the conjugate base produces rounded branch vertices rather than sharp linear intersections, requiring extrapolation from points well outside the equivalence zone.'] The conductometric titration of an acid mixture is governed by electrolytic conduction theory, Kohlrausch's law of independent ionic migration, and chemical equilibrium thermodynamics. As standardized sodium hydroxide is progressively added, the titration proceeds through three distinct chemical regimes: (1) neutralization of hydrochloric acid, where highly mobile hydronium ions (λ° = 349.8 S·cm²·mol⁻¹) are consumed and replaced by sodium ions (λ° = 50.11 S·cm²·mol⁻¹), generating a steep linear conductance drop (slope ≈ -0.355 mS·mL⁻¹); (2) neutralization of acetic acid, where unionized molecular CH₃COOH is converted into sodium acetate, steadily increasing conductance (slope ≈ +0.091 mS·mL⁻¹); and (3) addition of excess sodium hydroxide, where unreacted hydroxide ions (λ° = 198.6 S·cm²·mol⁻¹) cause a steep conductance rise (slope ≈ +0.249 mS·mL⁻¹). Applying the volume dilution correction factor G_corr = G_raw × (V_0 + V) / V_0 yields strictly linear segments whose intersections precisely define the equivalence volumes V_eq,1 and V_eq,2, enabling accurate determination of individual acid concentrations with relative uncertainties below 0.3%.
Analytical chemistry apparatus & tools.
Platinized Platinum Dip Cell
Paired parallel platinum plates (1.0 cm × 1.0 cm, electrode spacing 1.0 cm, cell constant K_cell = 1.000 cm⁻¹) electrolytically coated with high-surface-area platinum black to suppress capacitive electrode polarization.
Class A Precision Micro-Burette (50.00 mL)
Grade A borosilicate volumetric dispensing burette fitted with PTFE stopcock and 0.02 mL subdivisions for high-precision titration of standardized 0.1000 M NaOH titrant.
Thermostatic Double-Walled Titration Vessel
Water-jacketed cylindrical reaction beaker interfaced to a circulating closed-loop thermostatic water bath regulated at 25.00 ± 0.05 °C to eliminate thermal conductivity drift.
Digital Magnetic Stirrer with Submersible Flea
Synchronous brushless magnetic stirrer maintaining steady 350 RPM agitation for rapid hydrodynamic mixing between titrant additions without entraining atmospheric bubbles.
Class A Volumetric Pipettes & Standards
Certified 25.00 mL transfer pipette (tolerance ±0.03 mL), analytical grade primary standard potassium chloride (0.0100 M KCl) for cell constant verification, and carbon dioxide-free deionized water.
FOLLOW THE METHOD
A reason behind every step.
Determine the individual concentrations of hydrochloric acid (strong acid) and acetic acid (weak acid) in an unknown binary mixture by conductometric titration with standardized sodium hydroxide. Suggested independent volumetric settings: 1.0, 2.5, 4.0, 5.5, 7.0, 8.5 mL.
01
Conductivity Cell Calibration & Constant Verification
Rinse the dip-type platinized platinum cell thoroughly with triple-distilled deionized water and blot gently with lint-free optical paper. Immerse the cell into certified 0.0100 M KCl calibration standard equilibrated at 25.00 °C. Measure electrolytic conductivity κ_std = 1.4087 mS/cm and verify that the measured conductance confirms cell constant K_cell = 1.000 ± 0.005 cm⁻¹.
02
Titration Vessel Assembly & Analyte Loading
Pipette exactly 25.00 mL of the unknown binary acid mixture (containing hydrochloric acid and acetic acid) into the double-walled thermostatic cell. Add 75.00 mL of freshly boiled, cooled deionized water (initial volume V_0 = 100.0 mL) to ensure the platinum electrode plates are fully submerged by at least 15 mm.
03
Thermostatic Equilibration & Baseline Conductance Acquisition
Turn on circulating water bath at 25.00 ± 0.05 °C and engage the magnetic stirrer at 350 RPM. Allow the reaction mixture to achieve steady thermal equilibrium over 10 minutes. Record the initial unneutralized solution conductance G_0 on the digital meter.
04
Strong Acid Neutralization Titration (Branch 1)
Add standardized 0.1000 M NaOH titrant from the micro-burette in increments of 1.00 mL to 1.50 mL. After each addition, stir for 15 seconds to achieve chemical uniformity, pause stirring for 5 seconds to ensure quiescent liquid between electrode plates, and log the stable conductance reading G in mS.
05
Weak Acid Neutralization & Excess Base Titration (Branches 2 & 3)
Continue progressive titrant dispensing through the conductance minimum at V ≈ 10.0 mL. Observe the moderate upward conductance trajectory during acetic acid neutralization up to the second equivalence point at V ≈ 25.0 mL. Extend additions past the second break point up to 35.0 mL to define the steep excess hydroxide branch.
06
Dilution Correction & Multi-Branch Equivalence Point Extraction
Calculate corrected conductance G_corr = G × (V_0 + V) / V_0 for every titration point. Perform ordinary least-squares linear regressions on Branch 1 (strong acid) and Branch 2 (weak acid). Solve for the first equivalence volume V_eq,1 from the intersection, and determine the concentration of hydrochloric acid c_HCl = (V_eq,1 × c_NaOH) / V_aliquot.
YOUR NOTEBOOK · 0 OBSERVATIONS
Turn measurements into quantitative chemical insight.
Points are your recorded gravimetric observations. The regression line validates the linear mass-volume proportionality and extracts density.
ORDINARY LEAST-SQUARES FIT · m = ρ·V + m₀
G_{\text{corr}} = -0.3552 \cdot V + 5.202 \implies V_{\text{eq},1} = 10.00\text{ mL} \implies c_{\text{HCl}} = 40.00\text{ mM}
| # | Sodium Hydroxide Titrant Volume V (mL) | Measured Electrolytic Conductance G_raw (mS) | Titrant Volume V (mL) | Corrected Conductance G_corr (mS) | Remove |
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