Definitions Flashcards
(13 cards)
What is first ionisation energy?
The energy required for the removal of 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of a gaseous 1+ ion
What is meant by conservation of energy?
Heat energy transferred between chemical system and surroundings
What is activation energy?
The minimum energy required for a reaction to take place
What is the enthalpy change of reaction?
Enthalpy change associated with a stated equation in the molar quantities shown in the equation, reactants and products in their standard states
What is enthalpy change of formation?
Enthalpy change when 1 mole of a compound is formed from its elements under standard conditions
(100kPa, 298k/25•C, 1 mol dm-3)
(the enthalpy of formation of an element in its standard state is zero)
What is enthalpy change of combustion?
Enthalpy change when 1 mole of a substance reacts completely with oxygen , under standard conditions (enthalpies of combustion always have negative values, as combustion is an exothermic reaction)
What is enthalpy change of neutralisation?
Enthalpy change when an acid reacts with a base to form 1 mole of H2O under standard conditions
Enthalpy change neut = -57kJ mole-1 Value the same for all neutralisation reactions involving:
H+(aq) + OH-(aq) -> H2O(l)
What is average bond enthalpy?
The energy required to break one mole of bonds in gaseous molecules
What is rate of reaction?
How fast a reactant is used up, or how fast a product is formed
What is a catalyst?
A catalyst increases reaction rate without being used up by the reaction by allowing a reaction to proceed via a different route with lower activation energy so that a greater proportion of molecules have energy which exceeds the activation energy
What is a homogeneous catalyst?
A reaction in which the catalyst and reactants are in the same ohysical state. Catalyst reacts with reactants to form an intermediate. Intermediate breaks down to form a product and catalyst is regenerated
Example: ozone depletion by chlorine radicals from Cl=C’s = homogeneous
What is a heterogenous catalyst?
A reaction in which the catalyst has a different physical state from the reactants. Catalyst, usually solid, in contact with gas or solution reactants.
Example: Iron (habor process) (solid) + ammonia (gas) = Heterogeneous
What is dynamic equilibrium?
Exists in a closed system, when the rate of forward reaction is equal to the rate of the reversed and the concentrations of reactants and products do not change
