AP Chemistry Chapter 6 & 17 Practice Test Flashcards

Vocabulary practice flashcards generated from the AP Chemistry Chapter 6 & 17 Practice Test covering thermodynamics, thermochemistry, enthalpy, entropy, Gibbs free energy, and heating curves.

First Law of Thermodynamics

The law stating that total energy remains constant in an isolated system, such as ice added to hot water in a rigid, insulated container with no heat exchange with the surroundings.

Third Law of Thermodynamics

The principle stating that the entropy of a pure, perfect crystal at absolute zero ($0\,K$) is equal to zero.

Standard Enthalpy of Reaction ($\Delta H^\circ$)

The change in enthalpy for a chemical reaction under standard conditions, calculated as the sum of standard enthalpies of formation of products minus reactants ($\Delta H^\circ = \sum \Delta H^\circ_f(\text{products}) - \sum \Delta H^\circ_f(\text{reactants})$).

Thermodynamically Unfavored at Low Temperatures but Favored at High Temperatures

A condition occurring when a reaction has an endothermic enthalpy change ($\Delta H^\circ > 0$) and a positive entropy change ($\Delta S^\circ > 0$), such as $2\,H_2O(g) \rightarrow 2\,H_2(g) + O_2(g)$ ($\Delta H^\circ = 484\,kJ/mol_{rxn}$ and $\Delta S^\circ = 90.0\,J/(mol_{rxn}K)$).

Enthalpy of Sublimation

The heat change required to convert one mole of a substance directly from the solid phase to the gas phase ($I_2(s) \rightarrow I_2(g)$), which can be determined using Hess's Law from component reactions.

Methane Heating Curve

A plot showing temperature changes and phase changes as heat is added to methane, where segment Q represents melting with $\Delta H_{fus} = 0.94\,kJ/mol$ and segment S represents vaporization with $\Delta H_{vap} = 8.2\,kJ/mol$.

Limiting Reactant

The substance in a chemical reaction that is completely consumed first and dictates the total amount of product produced and total heat released ($q$).

Specific Heat Capacity ($c$)

The amount of heat energy required to raise the temperature of one gram of a substance by one degree Celsius (or Kelvin), expressed in units of $J/(g \cdot ^\circ C)$.

Gibbs Free Energy Equation

The relationship $\Delta G^\circ = \Delta H^\circ - T\Delta S^\circ$ that determines the thermodynamic favorability of a process at a given temperature $T$.

Thermal Equilibrium

The state reached when two objects or system components in thermal contact cease to exchange heat and reach the same temperature.

Enthalpy of Fusion ($\Delta H_{fus}$)

The enthalpy change associated with melting a solid into a liquid at its melting point without a change in temperature.

Enthalpy of Vaporization ($\Delta H_{vap}$)

The enthalpy change associated with vaporizing a liquid into a gas at its boiling point without a change in temperature.

$\Delta G^\circ$ vs. Temperature Linear Relationship

Graphical representation of Gibbs free energy as a function of temperature where the y-intercept represents $\Delta H^\circ$ and the slope equals $-\Delta S^\circ$.