Vacuum-Insulated Double-Walled Dewar Calorimeter
Provides a high-efficiency thermal enclosure with mirrored inner walls and an evacuated envelope, minimizing radiative and conductive heat exchange between the chilled solution and ambient room air.
Chemistry / Heat of Solution Calorimetry
FREE TO EXPLORELABORATORY 14 · NATURAL SCIENCES
Calorimetric Determination of the Integral and Differential Heat of Solution of Electrolytes
Determine the standard molar integral enthalpy of solution (ΔH_soln°) of crystalline potassium nitrate (KNO3) in water using an insulated solution calorimeter, evaluate the endothermic balance between crystal lattice energy and ion hydration enthalpies, extrapolate Newton ambient re-warming curves, and extract 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 DEPRESSION ΔT_DROP—
MEASUREMENT STATUS
Ready to dispense 4.0 g of liquid.
Adjust solute mass 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 calculation assumes that the specific heat capacity of dilute potassium nitrate solutions remains close to pure water (4.184 J/(g·K)), that non-adiabatic heat leakage is strictly linear and governed by Newton's law of cooling over the 1.5–5.5 °C temperature drop, and that complete crystal dissolution occurs before the post-period re-warming extrapolation baseline begins. Trace heat of immersion of the crystal surface is negligible (<0.1%) and absorbed into the regression intercept. The physical chemistry simulation model is based on the constant-pressure solution calorimetric relation ΔT_drop = −ΔT = [ ΔH_soln / (M_KNO3 · C_eff) ] · m + ΔT₀. System constants: potassium nitrate formula molar mass M_KNO3 = 101.103 g/mol; deionized water solvent charge m_water = 100.00 g (specific heat capacity c_p = 4.184 J/(g·K)), Dewar calorimeter vessel body heat capacity C_cal = 27.5 J/K. Total calorimeter system effective heat capacity: C_eff = m_water · c_p + C_cal = 100.0 · 4.184 + 27.5 = 445.90 J/K = 0.44590 kJ/K. Accepted literature integral molar enthalpy of solution at infinite dilution: ΔH_soln° = +34.890 kJ/mol. Theoretical thermometric slope: m_slope = ΔH_soln / (M_KNO3 · C_eff) = 34.890 / (101.103 · 0.44590) = 0.773926 °C/g. For potassium nitrate crystal masses from m = 2.000 g to 7.000 g, adiabatic temperature depressions span ΔT_drop = 1.548 °C to 5.417 °C. Linear regression across the series isolates ΔH_soln with R² = 1.00000; any constant thermal effect from mechanical stirring friction or initial salt temperature offset is absorbed into the regression intercept ΔT₀.
Analytical chemistry apparatus & tools.
NIST-Traceable Digital Thermistor Thermometer (±0.001 °C)
Continuously logs high-resolution temperature readings at 2 Hz during the pre-period baseline, rapid endothermic temperature plunge, and post-dissolution ambient re-warming curve.
Motorized PTFE Paddle Stirrer (200 rpm)
Ensures rapid, reproducible convective dissolution of the crystalline salt throughout the 100 mL water volume while maintaining minimal, steady mechanical heat dissipation.
Analytical Four-Decimal Balance (±0.0001 g)
Accurately weighs dry, recrystallized potassium nitrate crystals to establish precise stoichiometric solute molar quantities.
Class-A Volumetric Pipette (100.00 ± 0.05 mL)
Dispenses exact 100.00 mL charges of distilled, deionized water into the calorimeter cell ensuring identical solvent heat capacities across trials.
Powder Funnel and Desiccator Storage Chamber
Stores dried analytical-grade KNO3 crystals over anhydrous silica gel to prevent atmospheric moisture absorption, and facilitates rapid, loss-free transfer into the calorimeter port.
FOLLOW THE METHOD
A reason behind every step.
Determine the standard molar integral enthalpy of solution (ΔH_soln°) of crystalline potassium nitrate (KNO3) in water using an insulated solution calorimeter, evaluate the endothermic balance between crystal lattice energy and ion hydration enthalpies, extrapolate Newton ambient re-warming curves, and extract molar enthalpy using ordinary least-squares regression. Suggested independent volumetric settings: 2.0, 3.0, 4.0, 5.0, 6.0, 7.0 g.
01
Calorimeter Preparation and Solvent Dispensing
Clean and dry the inner glass Dewar vessel. Using a calibrated Class-A volumetric pipette, dispense exactly 100.00 ± 0.05 mL of deionized water (equilibrated to ambient room temperature) into the calorimeter. Seal with the PTFE lid and assemble the thermistor and paddle stirrer.
02
Potassium Nitrate Crystal Gravimetry
Take dried, analytical-grade crystalline potassium nitrate from the desiccator. Accurately weigh the assigned mass (between 2.0000 g and 7.0000 g) on the analytical balance using a glazed weighing paper or weighing boat to ±0.0001 g.
03
Pre-Dissolution Thermal Baseline Acquisition
Activate the motorized stirrer at 200 rpm. Record the calorimeter water temperature at 10-second intervals for 5 minutes (300 s) to establish a stable pre-period thermal drift baseline (dT/dt < 0.001 °C/min).
04
Solute Introduction and Endothermic Dissolution
Quickly open the PTFE lid addition port, transfer the weighed potassium nitrate crystals quantitatively into the water using the powder funnel, and immediately reseal the port. Monitor the rapid endothermic temperature drop as the crystals dissolve under continuous stirring.
05
Post-Dissolution Re-Warming Tracking
After reaching minimum temperature (maximum depression), continue logging thermistor readings every 10 seconds for at least 10 minutes (600 s) to capture the linear Newton re-warming slope from ambient room air.
06
Extrapolation, Enthalpy Computation and Regression
Plot the thermogram. Extrapolate the pre-period baseline and post-period re-warming line to the 63.2% dissolution time to isolate the corrected adiabatic temperature depression ΔT_drop. Calculate ΔH_soln = (C_eff · ΔT_drop) / n_solute, and perform linear regression across all six mass trials to extract ΔH_soln°.
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_drop = [ΔH_soln / (M_KNO3 · C_eff)] · m + ΔT₀ ==> ΔT_drop = 0.774 · m
| # | Potassium nitrate mass m (g) (g) | Adiabatic temperature depression ΔT_drop (°C) | Potassium nitrate mass m (g) | Corrected temperature depression ΔT_drop (°C) | Remove |
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