Chem H: Thermochemistry Formulas Flashcards

Heat Capacity Formula: ( q = C \times \Delta t )
- ( C ) represents heat capacity in Joules per degree Celsius (J/ºC).
- ( \Delta t ) is the change in temperature computed as final temperature minus initial temperature.
Heat Flow Formula: ( q = m \times c \times \Delta t )
- ( m ) stands for mass, ( c ) is the specific heat, and ( \Delta t ) is the temperature change.
Specific Heat of Water:
- Water has a specific heat of 4.18 J/gºC, essential for calculations involving heat transfer.
Heat Transfer in Reactions:
- The relationship ( q_{\text{reaction}} = -q_{\text{calorimeter}} ) indicates that the heat exchanged by the reaction is equal in magnitude but opposite in sign to the heat measured in the calorimeter.
Bomb Calorimeter Equation:
- ( q_{\text{reaction}} = -C_{cal} \times \Delta t ) can determine the heat absorbed or released in a reaction using known calorimeter heat capacity and temperature change.

Hess's Law:
- ( \Delta H = \Delta H_1 + \Delta H_2 ) asserts that the total enthalpy change for a reaction is the sum of the changes for individual steps.
Enthalpy Change at Constant Pressure:
- ( q_{\text{reaction}} ) at constant pressure equals ( \Delta H ), where ( \Delta H ) is the difference in enthalpy between products and reactants.
Standard Enthalpy Change:
- Calculated using the formula ( \Delta H^\circ = \sum \Delta H^\circ_f \text{(products)} - \sum \Delta H^\circ_f \text{(reactants)} ).

Conservation of Energy:
- The equation ( \Delta E_{\text{system}} = -\Delta E_{\text{surroundings}} ) embodies the principle that energy lost by one system is gained by another.
First Law of Thermodynamics:
- Expressed as ( \Delta E = q + w ) where total energy change equals the sum of heat flow and work done.

Heat Flow and Enthalpy:
- At constant pressure, ( \Delta H = q_p ) shows that heat flow is directly related to changes in enthalpy.
Constant Volume Heat Flow:
- At constant volume, ( \Delta H = q_v ) still maintains a direct relationship between heat flow and enthalpy.
Change in Enthalpy and Energy:
- ( \Delta H = \Delta E + \Delta(PV) ) links changes in enthalpy to changes in energy and the product of pressure and volume.
Relation between Enthalpy and Energy Change:
- ( \Delta H = \Delta E + \Delta n_g RT ) describes how enthalpy change correlates to energy change plus adjustments for changes in gas moles at temperature ( T ), with R as the ideal gas constant (8.31 J/mol K).