Thermostatted Reciprocal Shaker Bath (25.0 °C)
Water bath shaker with digital temperature controller (25.0 ± 0.1 °C) and variable agitation speed (150 rpm) to equilibrate six 250 mL stoppered Erlenmeyer flasks.
Chemistry / Freundlich Adsorption on Charcoal
FREE TO EXPLORELABORATORY 48 · NATURAL SCIENCES
Adsorption of Acetic Acid on Activated Charcoal and Evaluation of the Freundlich and Langmuir Isotherms
Determine the adsorption isotherm of aqueous acetic acid on activated charcoal at 25.0 °C and evaluate the Freundlich adsorption parameters (exponent 1/n and capacity constant K_F) and Langmuir parameters. Explore interactive analytical gravimetry, Class A volumetric glassware and density determination.
MEASURE · CALIBRATE · ANALYSE
Your virtual chemistry laboratory.
SPECIFIC ADSORPTION CAPACITY Q = X/M—
MEASUREMENT STATUS
Ready to dispense 0.12 M of liquid.
Adjust C_eq 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
["The empirical Freundlich isotherm does not predict a finite saturation capacity at high concentrations (x/m approaches infinity as C_eq -> infinity), unlike Langmuir's asymptotic limit.", "At very low concentrations (C_eq < 0.005 M), the Freundlich model fails to reduce to Henry's law (linear adsorption), overestimating uptake.", 'Titrimetric quantification with phenolphthalein assumes all titratable acidity originates from acetic acid, neglecting minor leaching of surface acidic carbon functional groups.'] The physical chemistry simulation model evaluates the adsorption of aqueous acetic acid (CH3COOH, M = 60.05 g/mol) onto acid-washed activated charcoal (m = 2.000 g, V = 100.0 mL = 0.1000 L) at 25.0 °C (298.15 K). Theoretical Freundlich parameters: capacity parameter K_F = 2.500 mmol/g · (L/mol)^(1/n), heterogeneity exponent 1/n = 0.4500 (n = 2.222). Across the six equilibrium concentration coordinates C_eq = [0.030, 0.060, 0.120, 0.220, 0.350, 0.550] M, the corresponding specific adsorption capacities are q = x/m = [0.516, 0.705, 0.963, 1.265, 1.559, 1.910] mmol/g. Logarithmic coordinates are x = log10(C_eq) = [−1.5229, −1.2218, −0.9208, −0.6576, −0.4559, −0.2596] and y = log10(x/m) = [−0.2874, −0.1519, −0.0164, 0.1020, 0.1928, 0.2811]. Ordinary least-squares regression yields an empirical slope 1/n = 0.45002 and Y-intercept log10(K_F) = 0.39795 (K_F = 2.500 mmol/g) with Pearson correlation coefficient R² = 0.999999990. The empirical exponent 1/n = 0.450 exhibits near-perfect concordance within 0.005% of the 0.450 literature benchmark, confirming favorable physical adsorption on a heterogeneous microporous carbon matrix.
Analytical chemistry apparatus & tools.
Acid-Washed Activated Coconut Charcoal Adsorbent
High-surface-area microporous activated charcoal (BET surface area > 950 m²/g, particle size 50–100 mesh, dried at 110 °C for 4 hours to remove pre-adsorbed volatiles).
Class-A Precision Automatic Burette (50.00 mL)
Precision 50.00 mL Class-A burette with PTFE stopcock (subdivisions 0.05 mL, readability ±0.02 mL) for titrimetric quantification of equilibrium acetic acid filtrates.
Standardized Sodium Hydroxide Titrant (0.1000 M)
Volumetric standard NaOH solution (0.1000 ± 0.0002 M) standardized against analytical primary standard potassium hydrogen phthalate (KHP) using phenolphthalein indicator.
Glacial Acetic Acid Stock Standard Series
High-purity acetic acid (CH3COOH, purity ≥ 99.7%, M = 60.05 g/mol) prepared in CO2-free deionized water to make initial standard solutions spanning 0.050 to 0.750 M.
Whatman No. 42 Ashless Quantitative Filter Paper & Funnels
Fluted quantitative filter paper cones and glass funnels pre-rinsed with deionized water to isolate clear aqueous filtrates from the activated charcoal slurry without acid retention.
FOLLOW THE METHOD
A reason behind every step.
Determine the adsorption isotherm of aqueous acetic acid on activated charcoal at 25.0 °C and evaluate the Freundlich adsorption parameters (exponent 1/n and capacity constant K_F) and Langmuir parameters. Suggested independent volumetric settings: 0.03, 0.06, 0.12, 0.22, 0.35, 0.55 M.
01
Massing of Activated Charcoal and Initial Solution Preparation
Accurately weigh six 2.000 ± 0.001 g samples of dried activated charcoal on an analytical balance and transfer into six clean, dry 250 mL glass-stoppered Erlenmeyer flasks labelled 1 through 6. Prepare 100.0 mL portions of standardized acetic acid solutions with initial concentrations C0 = 0.050, 0.100, 0.200, 0.350, 0.500, and 0.750 M in Class-A volumetric flasks.
02
Addition of Acid Solutions and Thermostatic Shaker Equilibration
Add exactly 100.0 mL of each acetic acid solution to the corresponding charcoal flask. Firmly insert ground-glass stoppers, secure flasks in the clamps of the thermostatted water bath shaker at 25.0 ± 0.1 °C, and agitate at 150 rpm for 90 minutes to ensure heterogeneous solid-liquid adsorption equilibrium is completely established.
03
Filtration and Rejection of Initial Column Wash Filtrate
Filter each equilibrated suspension through dry Whatman No. 42 quantitative filter paper into clean, dry Erlenmeyer flasks. Discard the first 15 mL of filtrate from each flask to eliminate experimental errors caused by minor preferential adsorption of acetic acid or water by the cellulose filter paper matrix.
04
Quantitative Titrimetric Analysis of Residual Acetic Acid
Pipette duplicate aliquots of the clear equilibrium filtrate (20.00 mL for flasks 1–3; 10.00 mL for flasks 4–6) into clean 125 mL titration flasks. Add 3 drops of 0.1% phenolphthalein indicator and titrate with standardized 0.1000 M NaOH until the persistent faint pink endpoint (stable for > 30 seconds). Record burette volumes to ±0.02 mL.
05
Calculation of Equilibrium Concentration and Specific Adsorption
Determine the equilibrium concentration C_eq = (V_NaOH · M_NaOH) / V_aliquot in mol/L. Compute the total millimoles of acetic acid adsorbed: x = (C0 − C_eq) · V_total (where V_total = 100.0 mL = 0.1000 L). Calculate the specific adsorption capacity q = x / m (in mmol of acetic acid adsorbed per gram of charcoal).
06
Linear Regression and Freundlich Isotherm Model Evaluation
Evaluate the logarithmic coordinates X = log10(C_eq) and Y = log10(x/m) for all six flasks. Execute ordinary least-squares linear regression to determine the slope (Freundlich heterogeneity exponent 1/n) and Y-intercept (log10 K_F). Evaluate the correlation coefficient R² and compare with the linearized Langmuir model (C_eq/q vs C_eq) to confirm the heterogeneous nature of the charcoal surface.
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
\log_{10}(x/m) = \log_{10} K_F + \left(\frac{1}{n}\right) \log_{10} C_{\text{eq}} \implies \frac{1}{n} = 0.450
| # | Equilibrium Acetic Acid Concentration C_eq (M) | Specific Adsorption Capacity q = x/m (mmol/g) | Log Equilibrium Concentration log₁₀(C_eq) | Log Specific Adsorption log₁₀(x/m) | Remove |
|---|
No readings yet. Dispense and weigh a volumetric aliquot to record it.
Calculate it yourself.
CHECK YOUR UNDERSTANDING