WK01

• What is the definition of exothermic?

  Heat is given out to the surroundings (the reactants lose energy).
• What is the definition of endothermic?

  Heat is taken in from the surroundings (the reactants gain energy).
• What is the definition of activation energy?

  The minimum energy required to start a reaction by the breaking of bonds.
• What is the definition of standard conditions?

  A pressure of 100kPa (1 atmosphere), a stated temperature, usually 298K (25C) and a concentration of 1.0mol/dm3 (for reactions with aqueous solutions).
• What is the definition of standard enthalpy change of reaction?

  The enthalpy change that accompanies a reaction in the molar quantities expressed in a chemical equation (under standard conditions, all reactants and products being in their standard states).
• What is the definition of standard enthalpy change of formation?

  The enthalpy change that takes place when one mole of a compound is formed from its constituent elements (in their standard states under standard conditions).
• What is the definition of standard enthalpy change of combustion?

  The enthalpy change that takes place when one mole of a substance reacts completely with oxygen (under standard conditions, all reactants and products being in their standard states).
• What is the definition of average bond enthalpy?

  The average energy change that takes place when breaking, by homolytic fission, 1 mol of a given type of covalent bond in the molecules of a gaseous species.
• What is the definition of enthalpy change of neutralisation?

  The energy change that accompanies the neutralisation of an aqueous acid by an aqueous base to form one mole of water under standard conditions.
• What is the definition of a catalyst?

  A catalyst speeds up a reaction without being consumed by the overall reaction.
• What is the definition of a dynamic equilibrium?

  The equilibrium that exists in a closed system when the rate of the forward reaction is equal to the rate of the reverse reaction.
• What is the definition of le Chatelier's Principle?

  When a system in dynamic equilibrium is subject to change, the position of equilibrium will shift to minimise the change.