AP Chemistry thermodynamics concepts such as enthalpy, entropy, and free energy, plus electrochemistry including redox and galvanic cells.
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- Define enthalpy
- The heat energy of a system, equal to the internal energy plus the product of pressure and volume (H = U + PV)
- Define entropy
- A measure of disorder or the number of possible arrangements of particles in a system
- What is Gibbs free energy?
- The maximum useful work a system can perform at constant temperature and pressure, calculated as ΔG = ΔH - TΔS
- A reaction is spontaneous at all temperatures when
- ΔH is negative and ΔS is positive (ΔG is always negative)
- An exothermic reaction is one where
- Energy is released to the surroundings, so ΔH is negative
- An endothermic reaction is one where
- Energy is absorbed from the surroundings, so ΔH is positive
- Define heat capacity
- The amount of heat energy required to raise the temperature of a substance by one degree
- State Hess's Law
- The enthalpy change of a reaction is the same regardless of the pathway taken, depending only on initial and final states
- What is standard enthalpy of formation?
- The enthalpy change when one mole of a compound is formed from its elements in their standard states
- Entropy increases when a system
- Becomes more disordered or dispersed, as occurs during phase changes from solid to liquid to gas, or dissolution, or mixing
- ____ equals zero at equilibrium
- ΔG
- At high temperatures, an endothermic reaction with positive entropy change becomes
- Spontaneous, because the TΔS term dominates the ΔH - TΔS equation
- Define oxidation
- Loss of electrons or an increase in oxidation state
- Define reduction
- Gain of electrons or a decrease in oxidation state
- What is the oxidation state of oxygen in most compounds?
- Minus 2, except in peroxides where it is minus 1 and in OF2 where it is plus 2