Enthalpy Changes Flashcards
What is enthalpy?
The heat content that is stored in a chemical system
What is exothermic?
A reaction in which the enthalpy of the products is smaller than the enthalpy of the reactants, resulting in heat loss to surroundings
What is endothermic?
A reaction in which the enthalpy of the products is greater than the enthalpy of the reactants, resulting in heat being taken in from surroundings
What is standard state?
Physical state of a substance under standard conditions of 100kPa and 298K
What is the standard enthalpy change of a reaction?
The enthalpy change that accompanies a reaction in molar quantities expressed in a chemical equation under standard conditions, all products and reactants being in their standard states
What is the standard enthalpy change of combustion?
Enthalpy change when one mole of a substance reacts completely with O2 under standard conditions, all reactants and products in their standard states
What is the standard enthalpy change of formation?
Enthalpy change when one mole of a compound is formed from its constituent elements in their standard states under standard conditions
What is the standard enthalpy change of neutralisation?
Enthalpy change when one mole of water is formed in a neutralisation reaction
What is specific heat capacity?
Energy required to raise temperature of 1g of a substance by 1C
What is the average bond enthalpy?
The average bond enthalpy change when breaking by homolytic fission one mole of a given bond in molecules of a gaseous species
What is Hess’ law?
States if a reaction can take place by more than one route, and initial and final conditions are the same, total enthalpy change is the same for each route
In terms of bond breaking and making, outline exothermic reactions
Energy released in bond making is greater than energy taken in during bond breaking
In terms of bond breaking and making, outline endothermic reactions
Energy released in bond making is less than energy taken in during bond breaking
