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Define exothermic process.
A process that releases heat to the surroundings; \(\Delta H\) is negative.
Define endothermic process.
A process that absorbs heat from the surroundings; \(\Delta H\) is positive.
What is the First Law of Thermodynamics?
Energy is conserved; it cannot be created or destroyed, only transferred or converted.
Define thermal equilibrium.
The state where heat flows until two objects reach the same temperature.
Define heat capacity.
The energy needed to raise 1 gram of a substance by 1 degree Celsius (J/g°C).
Define enthalpy (\(\Delta H\)).
The heat change at constant pressure; indicates whether a reaction is exothermic or endothermic.
Define enthalpy of formation (\(\Delta H_f^\circ\)).
The heat change when one mole of a compound is formed from its elements in their standard states.
What is a state function?
A property whose value does not depend on the path taken to reach a specific value.
Describe the process of calorimetry.
Measure the initial temperature of reactants and calorimeter, conduct the reaction inside the calorimeter, measure the final temperature, and calculate the heat released or absorbed using \(q = mc\Delta T\).
How do you calculate enthalpy using bond enthalpies?
Sum of bond energies broken minus the sum of bond energies formed: \(\Delta H = \Sigma \text{Bonds Broken} - \Sigma \text{Bonds Formed}\).
How do you calculate enthalpy using enthalpies of formation?
Sum of enthalpies of formation of products minus the sum of enthalpies of formation of reactants: \(\Delta H = \Sigma \Delta H_f^\circ \text{(Products)} - \Sigma \Delta H_f^\circ \text{(Reactants)}\).
Explain Hess's Law.
If a reaction can be expressed as a series of steps, the enthalpy change for the overall reaction is the sum of the enthalpy changes for each step. Manipulate individual reactions (reversing or multiplying) to match the target reaction.
Differentiate between exothermic and endothermic reactions in terms of \(\Delta H\) and heat flow.
Exothermic: \(\Delta H < 0\), heat is released. Endothermic: \(\Delta H > 0\), heat is absorbed.
Compare calculating \(\Delta H\) using bond enthalpies versus enthalpies of formation.
Bond Enthalpies: Uses bond breaking and forming energies. Enthalpies of Formation: Uses standard enthalpies of formation of products and reactants.