4 - Energetics Flashcards
What are exothermic and endothermic reactions
Exothermic is where energy is given out, endo-, when energy it taken in
What is enthalpy
The energy given out when a substance is reacted under standard conditions
What is the standard molar enthalpy of formation
The enthalpy change when one mole of substance is formed from its constituent elements under standard conditions, all reactants and products being in their standard states
What is the standard molar enthalpy of combustion
The enthalpy change when one mole of substance is completely burnt in oxygen under standard conditions, all reactants and products being in their standard states
What is the specific heat capacity
The heat required to change the temperature of 1 g of substance by 1 K in J /g /K
What is the equation relating temperature to SHC
q = MC T
What is Hess’s law
Hess’s law states that the enthalpy change for a chemical reaction is the same, whatever route is taken from reactants to product
What are the five ways of changing the rate of a chemical reaction
Temperature
Concentration
Pressure
Surface area
Using a catalyst
What is the activation energy of a reaction
The energy required to form the transition state, which can then form the products
What do catalysts do
they allow a different transition state to be formed with a lower activation energy, thus increasing the rate of the reaction
