Energy Diagrams - AP Chemistry

Identify the energy difference from reactants to peak. Measure vertical distance from start to peak.

The difficulty of initiating the reaction. Higher barrier means slower reaction rate.

Difference in energy between reactants and products. Vertical distance between reactant and product levels.

It is the highest energy state, representing a critical point. Unstable state where bond breaking and forming occur.

The difference in energy from reactants to transition state. Vertical distance from reactants to the peak.

Lower peaks, but reactants and products remain unchanged. Same $\triangle H$ but alternative lower-energy pathway.

Lower activation energy. Easier pathway increases reaction rate.

The highest energy barrier between intermediates. The step with highest activation energy controls rate.

Multiple peaks and valleys. Each peak represents a separate elementary step.

Reaction coordinate. Shows the progress of the reaction from start to finish.

Potential energy. Represents the energy content of species during reaction.

The energy required to initiate a reaction. Minimum energy needed for reactants to form products.

Exothermic. Energy flows out when products form at lower energy.

Temperature does not change the diagram shape but can affect rates. Affects kinetics but not thermodynamic energy levels.

As valleys between peaks. Local minima between transition state peaks.

Slower reaction rate due to higher activation energy. Higher energy barrier reduces reaction rate significantly.

Positive. Products are higher in energy than reactants.

In multi-step reactions, between transition states. Formed at energy minima between reaction steps.

Subtract reactant energy from product energy. Calculate final minus initial energy levels.

Both forward and reverse activation energies are shown. Can proceed in either direction with different barriers.

Pressure does not alter energy diagram shape. Energy levels remain constant regardless of pressure.

Two activation energies: one for forward, one for reverse. Different energy barriers for each reaction direction.

Negative. Products are lower in energy than reactants.

Intermediate. A stable species formed temporarily during the reaction.

A stable intermediate or plateau in energy change. Shows constant energy region or stable intermediate.

Exothermic: products lower; Endothermic: products higher. Based on final energy relative to starting energy.

Endothermic. Energy must be added when products are higher energy.

It is not directly meaningful; focus on energy differences. Curve area doesn't represent meaningful energy quantity.

No specific width significance; focus on height. Width is not meaningful; only peak height matters.