Energetics and Reactivity Flashcards

Flashcards on Energetics and Reactivity

bond enthalpy refers to

The energy required to break one mole of chemical bonds in the gaseous state.Bond enthalpy values are always positive because they refer to bonds being broken (bond breaking is endothermic)

Enthalpy Change (ΔH)

The overall change in heat content during a chemical reaction.

Endothermic Reaction

A chemical reaction that absorbs energy from the surroundings.

Exothermic Reaction

A chemical reaction that releases energy to the surroundings.

Combustion Reaction

A type of reaction that is always exothermic, involving burning in the presence of oxygen.

Acid-base Neutralization Reaction

A type of reaction that is always exothermic, involving the reaction between an acid and a base.

Heat (q)

The total energy of a system's particles.

Temperature

The average kinetic energy of a system's particles.

Specific Heat Capacity (c)

The amount of heat required to raise the temperature of a substance.

Calorimetry

A technique used to measure the enthalpy associated with a particular change.

Bond Enthalpy

The energy required to break one mole of a particular covalent bond in the gaseous phase.

Average Bond Enthalpy

The energy required to break the specific covalent bonds in one mole of gaseous molecules, separating them into gaseous atoms, averaged over similar compounds.

Hess’s Law

The enthalpy change for a reaction is independent of the pathway between the initial and final states.

Standard Enthalpy Change (ΔH⊖)

The heat transferred at constant pressure under standard conditions and states.

System

The specific part of the universe that is of interest in the study.

Surroundings

Everything outside the system.

Energy Profile

A diagram that shows the energy changes during the course of a reaction.

Q = mcΔT

Equation used to calculate the heat change of a substance.

ΔH = –Q/n

Equation used to calculate the enthalpy change of a reaction.

Bond Breaking

Requires energy input and is endothermic.

Bond Forming

Releases energy and is exothermic.

First Law of Thermodynamics

Energy cannot be created or destroyed.

Exothermic Reaction Temperature Change

Temperature increase in the surroundings.

Endothermic Reaction Temperature Change

Temperature decrease in the surroundings.

Enthalpy of Solution

The enthalpy change when one mole of a substance dissolves completely in solvent.

State Function

A function whose value depends only on the initial and final states, not on the path taken.

Breaking Stronger Bonds

Requires more energy input.

Making Stronger Bonds

Releases more energy.

ΔHreaction  (Hbonds broken) – (Hbonds formed)

Equation for approximating the enthalpy change of a reaction using bond enthalpies.

Enthalpy Cycle

A diagram that represents Hess's Law, showing enthalpy changes for different reaction pathways.

CoFDe (exo)

Condensation, Freezing, Deposition

when forming bonds,

energy is released, ( exothermic) the products are more stable. Think that they ahve a lower energy level