When are ΔH and ΔU identical in a combustion reaction?

When there is no net change in the number of moles of gas between products and reactants (Δn_g = 0), making the Δn_g*R*T correction term zero.

Bomb Calorimetry (ΔU & ΔH)Chemistry

Bomb Calorimeter Internal Energy (ΔU) & Enthalpy of Combustion Calculator

Calculate heat released, molar internal energy of combustion (ΔU), and standard enthalpy of combustion (ΔH) from constant-volume bomb calorimetry data.

Chemistry & Solutions Thermodynamics

Calculated Result

Standard Enthalpy of Combustion (ΔH)

-3,142.78kJ/mol

Calculator Inputs

Calorimeter Heat Capacity C_cal (kJ/°C)

kJ/°C

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Temperature Rise ΔT

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Sample Mass (grams)

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Sample Molar Mass M (g/mol)

g/mol

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Standard Enthalpy of Combustion (ΔH)

-3,142.78kJ/mol

Internal Energy of Combustion (ΔU)

-3,141.54 kJ/mol

Total Measured Heat Released

25.73 kJ

Highly Exothermic Combustion (ΔH < 0): High calorific energy release confirms strong fuel heating potency.

Internal Energy vs Enthalpy of Combustion

Internal Energy ΔU

-3,141.54 kJ/mol(0%)

Enthalpy ΔH

-3,142.78 kJ/mol(0%)

Standard physical chemistry and thermochemical analysis tool for fuel calorific value determination.

Calculation Methodology

Constant Volume Heat: q_cal = C_cal * ΔT. Molar Internal Energy: ΔU = -q_cal / n_sample. Enthalpy Conversion: ΔH = ΔU + (Δn_g * R * T / 1000). Where R = 8.314 J/(mol K) and Δn_g is gaseous stoichiometric moles change.

Frequently Asked Questions

Because the rigid steel bomb vessel maintains a strictly constant volume (ΔV = 0), precluding pressure-volume work (PΔV = 0) so that heat flow directly equals the change in internal energy (qv = ΔU).

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Chemistry

Bomb Calorimeter Internal Energy (ΔU) & Enthalpy of Combustion Calculator

Calculator Inputs

Internal Energy vs Enthalpy of Combustion

Calculation Methodology

Frequently Asked Questions

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