Flashcards in DF Deck (25):
reaction that gives out energy to the surroundings. delta H is - ve.
Energy released in making new bonds is greater than energy required to break existing bonds.
reaction that takes in energy from and cools the surroundings. delta H is + ve.
Energy released in making new bonds is less than energy required to break existing bonds.
1 atm pressure
1 mol dm-3 solutions
standard enthalpy change of reaction
enthalpy change when molar quantities of reactants as stated in the equation react together under standard conditions.
standard enthalpy change of combustion
enthalpy change when 1 mole of a substance is burnt completely in oxygen under standard conditions with elements in their standard states.
standard enthalpy change of formation
enthalpy change when 1 mole of a compound is formed from its elements under standard conditions in standard states.
standard enthalpy change of neutralisation
enthalpy change when 1 mole of H+ ions reacts with 1 mole of OH- ions to form 1 mole of water under standard conditions with 1 mol dm-3 solutions.
converting from celcius to kelvin and kelvin to celcius:
compounds which contain 1 or more benzene rings
compounds which do not contain any benzene rings
a compound formed of carbon and hydrogen atoms only
a modifier responsible for the characteristic chemical reactions of molecules.
hydrocarbons containing the maximum number of hydrogen atoms possible/ no C to C double or triple bonds.
a series of compounds which all have the same general molecular formula and functional group.
average bond enthalpy
average quantity of energy required to break 1 mole of a bond with substances in the gaseous state. kJ mol-1
any reaction in which a larger molecule is broken down into smaller molecules. E.g. cracking of alkanes to produce a shorter chain alkane and alkene.
an organic compound which contains a double or triple bond between carbon atoms.
a substance which increases the rate of a chemical reaction but is chemically unchanged at the end.
the process of using a catalyst to increase the rate of a chemical reaction.
the catalyst and reactants are in different physical states.
how does it function?
stops a catalyst from functioning properly as it adsorbs to the catalyst surface more strongly than the reactants. The reactants are prevented from adsorbing and the catalyst is unable to get involved with the reaction.
Process of heterogeneous catalysis
- reactant molecules adsorb to the catalyst surface.
- bonds within the reactant molecules weaken and break.
- new bonds form between the reactant atoms to form the products.
- the products desorb and diffuse away from the catalyst surface.
enthalpy change of formation of an element = ?
same molecular formula but different structural formula