Thermochemistry & Calorimetry Lab

Reaction

Calorimeter setup

Moles reacted 0.10 mol

Water mass 200 g

Calorimeter constant C_cal 10 J/°C

Live readout

Temperature

25.0 °C

ΔT

0.0 °C

Heat released, q

0 J

ΔH measured

– kJ/mol

Temperature vs. time since the reaction started.

How it works

The glowing capsule at the centre is the reaction vessel; the fluid around it is the calorimeter's water bath, stirred continuously so the whole bath reaches one uniform temperature. Choosing a reaction fixes its molar enthalpy ΔH (kJ/mol) — negative for exothermic, positive for endothermic. Pressing Start releases (or absorbs) heat q = −ΔH·n into the bath, which the calorimeter measures as a temperature change:

q = −ΔH · n
ΔT = q / (m_water·c_water + C_cal)
ΔH(measured) = −q / n

Moles reacted — amount of limiting reactant consumed, n.
Water mass — the bath absorbing the heat; c_water = 4.18 J/g·°C.
C_cal — heat capacity of the calorimeter's own walls/thermometer/stirrer, which also warms up alongside the water (why a real calorimeter is first calibrated with a known heat before it's trusted).

Orange particles streaming outward mean the reaction is exothermic and heating the bath (thermometer glows red, water tints warm); blue particles streaming inward mean it is endothermic and pulling heat out of the water (thermometer cools, water tints blue). By Hess's law the measured ΔH does not depend on the path the reaction takes to get from reactants to products — only on the difference between their enthalpies — which is exactly why a calorimeter can measure it directly from a single experiment.

Exothermic heat flow Endothermic heat flow Stirrer / thermometer

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