Energetics Flashcards
What is the conservation of energy?
Energy cannot be created or destroyed only stored or transferred
Chemical bonds are the forces of attraction the bind atoms together. They hold a potential energy.
Define enthalpy
The thermal energy that is stored in a chemical system.
What are the standard conditions for enthalpy reactions?
Pressure: 100KPa
Temperature: 298K
What is the system and what are the surroundings?
System- chemical reactions (atoms and bonds)
Surroundings- everything else
Define enthalpy change
The difference between the enthalpy of the products and the reactants
Change in enthalpy= Hproducts - Hreactants
What are exothermic reactions?
When the enthalpy of the products is lower than the enthalpy of the reactants and therefore heat energy has been lost to the surroundings
What are endothermic reactions?
When the enthalpy of the products is greater than the enthalpy of the reactants and therefore energy has been absorbed by the reactants to form bonds.
What is activation energy?
The minimum energy require to break bonds in the reactants for a reaction to take place
What is Hess’s law?
The enthalpy change of a reaction is independent of the route taken. It relies only on be initial and final states of the reaction.
Define the enthalpy change for a reaction.
The enthalpy change when the amounts of reactants show in the equation react under standard conditions to give their products in their standard states.
Define enthalpy change of formation.
The enthalpy hangs when 1 mole of a compound is formed from its elements in their standard states under standard conditions
Define the enthalpy change of combustion
The enthalpy change when 1 mole of a substance is burnt completely in Excess oxygen under standard conditions
Define enthalpy of change of neutralisation.
The enthalpy change when solutions of acid and alkali react together under standard conditions to produce 1 mole of water.
Define the enthalpy change of solution.
The enthalpy change when 1 mole of solute dissolved completely in sufficient solvent to form a solution in which the ions are far enough apart to not interact with each other.
Define the mean bond enthalpy
The mean /average energy required for 1 mole of a given type of gaseous bond to undergo homolytic fission