Energy and Reaction Rates Flashcards

Vocabulary flashcards covering chemical reaction energy, heats of reaction, energy diagrams, activation energy, and reaction rates.

Endothermic Process

A process in which a system gains heat from its surroundings, causing the temperature of the surroundings to decrease, associated with a positive sign ($+\Delta H$).

Exothermic Process

A process in which a system releases heat into its surroundings, causing the temperature of the surroundings to increase, associated with a negative sign ($-\Delta H$).

Heat of Reaction ($\Delta H$)

The change in energy that takes place during the course of a chemical reaction.

Combustion of Methane

An exothermic reaction in which each mole of methane ($CH_4$) burned releases $890.4\,kJ$ of energy, resulting in a $\Delta H$ of $-890.4\,kJ$.

Decomposition of Calcium Carbonate

An endothermic reaction where the decomposition of one mole of calcium carbonate requires the absorption of $177.8\,kJ$ of energy, resulting in a $\Delta H$ of $+177.8\,kJ$.

Reaction Rate

A measure of how fast a chemical reaction happens, which can be increased by raising the temperature, increasing reactant concentration, or adding a catalyst.

Energy Diagram

A single graph that summarizes important reaction energy information by plotting potential energy on the y-axis against reaction progress or time on the x-axis.

Transition State

The highest point in an energy diagram graph for a chemical reaction.

Activation Energy ($E_a$)

The difference in energy between the reactants and the transition state, which acts as a barrier to a reaction.

Catalyst

A substance that speeds up a reaction without being consumed or changed by providing an alternate reaction route with a lower activation energy.

Enzyme

A biological catalyst made up of proteins that increases reaction rates by decreasing activation energy.