Vacuum-Insulated Dewar Reaction Calorimeter
Silvered double-walled borosilicate glass Dewar vessel (internal volume 200 mL) fitted with a 20 mm expanded polystyrene insulation jacket and low-thermal-conductivity PTFE stopper.
Chemistry / Enthalpy of Neutralization
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Determination of the Enthalpy of Acid-Base Neutralization via Solution Calorimetry
Determine the standard molar enthalpy of neutralization (ΔH_neut°) for the reaction between strong acid (HCl) and strong base (NaOH) in an adiabatic constant-pressure solution calorimeter, evaluating heat loss correction kinetics, and extracting molar enthalpy using ordinary least-squares regression. Explore interactive analytical gravimetry, Class A volumetric glassware and density determination.
MEASURE · CALIBRATE · ANALYSE
Your virtual chemistry laboratory.
ADIABATIC TEMPERATURE RISE ΔT—
MEASUREMENT STATUS
Ready to dispense 0.04 mol of liquid.
Adjust moles neutralized 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 determination of the enthalpy of neutralization via solution calorimetry is subject to specific experimental constraints: (1) Non-Adiabatic Wall Heat Leakage: Even high-grade vacuum Dewar vessels exhibit finite thermal conductance, dissipating ~0.5% to 1.5% of peak heat during the reaction period. (2) Heat of Dilution Effects: In concentrated solutions (e.g. 2 M), ions possess non-negligible heats of dilution as they disperse into the reaction volume, slightly perturbing the pure hydronium-hydroxide combination enthalpy. (3) Calorimeter Water Equivalent Uncertainty: The heat capacity of the glass vessel, stirrer, and probe varies slightly with liquid level and immersion depth. (4) Reagent Transfer Dead Volume: Trace droplets adhering to volumetric pipette tips or delivery funnels can introduce slight stoichiometric deficits (<0.1%). The solution calorimetry physical model incorporates the relation ΔT = [ |ΔH_neut| / C_eff ] · n + ΔT₀. Experimental system constants: total solution volume V_total = 100.00 mL (dilute NaCl solution density ρ = 1.015 g/mL, mass m_soln = 101.5 g, solution specific heat capacity c_p = 4.10 J/(g·K)), calorimeter water equivalent heat capacity C_cal = 27.5 J/K. The effective heat capacity of the complete calorimetric system is C_eff = m_soln · c_p + C_cal = 101.5 · 4.10 + 27.5 = 443.65 J/K = 0.44365 kJ/K. Standard reference molar enthalpy of neutralization: ΔH_neut° = -55.84 kJ/mol. The theoretical regression slope is m_slope = |ΔH_neut| / C_eff = 55.84 / 0.44365 = 125.868 °C/mol. Across n = 0.020 to 0.070 mol, temperature rises span from 2.517 °C to 8.811 °C. Linear regression across varying stoichiometric loadings absorbs constant stirring heat (q_stir ≈ 0.02 J/s) or slight thermistor offset into the intercept ΔT₀ = 0.000 °C, ensuring that the regression slope represents the true, unbiased marginal enthalpy of reaction.
Analytical chemistry apparatus & tools.
Calibrated NIST Four-Wire Platinum RTD Sensor
Micro-immersion digital thermistor probe with 0.001 °C readability and 0.005 °C absolute accuracy, connected to a digital datalogger.
Motorized Variable-Speed PTFE Paddle Stirrer
Overhead synchronous electric motor driving a dual-blade PTFE propeller at 200 rpm to ensure instantaneous homogenization without viscous heating.
Class A Volumetric Pipettes & Burettes
25.00 mL and 50.00 mL volumetric pipettes (tolerance ±0.03 mL) to deliver precise stoichiometric volumes of 2.000 M HCl and 2.000 M NaOH.
Thermostated Reagent Equilibration Bath
Circulating water bath maintaining stock acid, base, and deionized water solutions at identical initial temperature (20.00 ± 0.02 °C).
Electric Calibration Heater & Precision Coulometer
Integrated 10.00 W nichrome immersion heating coil with regulated DC power supply to determine the calorimeter water equivalent C_cal via Joule heating.
FOLLOW THE METHOD
A reason behind every step.
Determine the standard molar enthalpy of neutralization (ΔH_neut°) for the reaction between strong acid (HCl) and strong base (NaOH) in an adiabatic constant-pressure solution calorimeter, evaluating heat loss correction kinetics, and extracting molar enthalpy using ordinary least-squares regression. Suggested independent volumetric settings: 0.02, 0.03, 0.04, 0.05, 0.06, 0.07 mol.
01
Calorimeter Constant (Water Equivalent) Determination
Deliver 50.00 mL of cold deionized water (15.0 °C) into the calorimeter, equilibrate for 5 minutes, record temperature every 30 seconds, then rapidly introduce 50.00 mL of warm water (35.0 °C) through the lid port. Extrapolate cooling curves to calculate the calorimeter constant C_cal = 27.5 J/K.
02
Stock Solution Preparation and Thermal Equilibration
Prepare standardized 2.000 M HCl and 2.000 M NaOH solutions. Immerse reagent flasks in a thermostatic bath at 20.00 °C for 30 minutes to eliminate pre-mixing temperature differences.
03
Calorimeter Charging
Charge the calorimeter with the specified aliquot of 2.000 M HCl and deionized water to bring the initial volume to exactly (100.00 - V_base) mL. Insert the thermistor probe and start the motorized stirrer.
04
Pre-Period Baseline Recording
Record the temperature of the initial acidic solution every 15 seconds for 3.0 minutes to establish the pre-reaction thermal drift slope (dT/dt)_pre.
05
Rapid Neutralization Injection and Post-Period Monitoring
Inject the stoichiometric volume of 2.000 M NaOH rapidly through the reagent port. Record temperature every 5 seconds through the steep temperature rise, followed by recordings every 15 seconds for 5.0 minutes to establish the post-period cooling drift (dT/dt)_post.
06
Adiabatic Extrapolation and Multi-Point Series
Extrapolate the pre- and post-period linear slopes to the mid-point of neutralization to extract the true corrected adiabatic temperature rise ΔT. Repeat across 0.020, 0.030, 0.040, 0.050, 0.060, and 0.070 mol of neutralized hydronium, and regress ΔT against n to determine ΔH_neut°.
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
ΔT = [|ΔH_neut| / C_eff] · n + ΔT₀ ==> ΔT = 125.87 · n
| # | Hydronium-hydroxide moles neutralized n (mol) (mol) | Adiabatic temperature rise ΔT (°C) | Moles of water formed n (mol) | Corrected temperature rise ΔT (°C) | Remove |
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