Energetics Flashcards
Definition of Enthalpy change for reaction
Enthalpy change when a reaction occurs in the molar quantities shown in the chemical equation
Under standard conditions with all reactants and products in their standard states
Definition of Enthalpy change of formation
Enthalpy change when 1 mole of a compounds is formed from its elements
Under standard conditions with all reactants and products in their standard states
Definition of Enthalpy change of combustion
Enthalpy change when a substance is completely burnt in oxygen
Under standard conditions with all reactants and products in their standard states
Definition of enthalpy change
Unit?
Heat energy change measured under conditions of constant pressure
kJmol-1
Equation for heat change (calorimetry)
Q =m x c x change in T
c is specific heat capacity
m is the mass of water
How do you find the enthalpy change of a substance using calorimetry?
- Use q = mct to find energy
- Find the moles of a substance that is reacting (use difference in mass)
- Divide energy by moles
What does Hess’s law state?
The total enthalpy change of a reaction is independent of the route taken
Definition of standard state
Normal physical state at 100kPa and 298K
What is the enthalpy change of formation of
- CO2
- H2O
the same as?
Enthalpy change of combustion of C
Enthalpy change of combustion of H
Define mean bond enthalpy
Average values of a number of compounds
What is the equation for bond enthalpy?
Unit?
Bond enthalpy = total bonds broken - total bonds formed
kJmol-1
