chapter 6 vocab Flashcards
Exothermic
Heat energy is released during a reaction. The value of ΔH is negative.
Endothermic
Heat energy is absorbed during the reaction. The value of ΔH is positive
Enthalpy change
The heat energy transferred during a chemical reaction
Reaction pathway diagram
Shows the relative enthalpies of the reactants and the products and the enthalpy change as an arrow. It may also include the activation energy.
Activation energy (Ea)
-The minimum energy that colliding particles must possess to break bonds to start a chemical reaction.
Standard conditions-
A pressure of 101kPa and a temperature of 298 K
Standard enthalpy change of reaction
the enthalpy change when the amount of reactants show in the stoichiometric equation react to give products under standard conditions
Standard enthalpy change of formation
- the enthalpy change when one mole of a compound is formed from its elements under standard conditions.
Standard enthalpy change of combustion
the enthalpy change when one mole of a substance is burnt in excess oxygen under standard conditions.
Standard enthalpy change of neutralization
the enthalpy change when one mole of water is formed by the reaction of an acid with an alkali under standard conditions.
️ Specific heat capacity
the energy needed to raise the temperature of 1g of a substance by 1 degree celsius / kelvin
Hess’s law-
the enthalpy change in a chemical reaction is independent of the route by which the chemical reaction takes place as long as the initial and final conditions and states of reactants and products are the same for each route.
exact bond enery
the energy needed to break a specific covalent bond in a named molecule in the gaseous state, e.g. the O-H bond in water. Also called the bond dissociation energy or bond enthalpy
average bond energies
the average energy needed to break a specific covalent bond averaged from a variety of molecules in the gaseous state, e.g. the average O-H bond energy in ethanol, water and other compounds
