Physical chem Flashcards
Combustion
one mole of substance is burned completely in oxygen
Formation
one mole of substance is produced from its constituent elements
Neutralisation
one mole of water is formed when acid and base react
Define bond enthalpy
Break same bond in all molecules in one mole of gase
Exo?
Bonds formed, temp rise
Endo?
Bonds broken, temp decrease
Hess’ law
If a reaction can take place by more than one route, the overall change is the same irrespective of route
Homogenous catalyst
Same phase a reactants
Heterogenous catalyst
Different phase
Absorbs gases on surface, weakens bonds decrease Ea, products are desorbed from surface
Why use catalysts?
Reduces temp and energy, no fossil fuel, lower atom economies reducing waste
Define dynamic eqm
Reached when rate of forward = backward
conc is constant
Define le chateliers system
Closed system at eqm is subject to change, system moves to minimise effect of change
Compromise
Low temp
High pressure
Compromise
