08 - equilibria Flashcards
reversible reaction
a reaction in which products can be changed back to reactants by reversing the conditions
equilibrium reaction
a reaction that does not go to completion and in which reactants and products are present in fixed concentration ratio
hydrogen and iodine reaction
H2 + I2 <=> 2HI
.sealed glass tube
. 400°C
equilibrium characteristics
. dynamic
. forward and reverse reactions occur at the same time
. concentrations of reactants and products remain constant at equilibrium
. closed system
closed system
a system in which matter is not lost or gained
dynamic equilibrium
reactants are being converted to products at the same rate as products are being converted back to reactants
Le Chatelier’s principle
if one or more factors that affect a dynamic equilibrium is changed, the position of equilibrium moves to minimise this change
Le Chatelier’s principle
if one or more factors that affect a dynamic equilibrium is changed, the position of equilibrium moves to minimise this change
factors affecting position of equilibrium
. concentration
. temperature
. pressure
CATALYSTS DON’T AFFECT
more pressure, position of equilibrium…
to less moles side
more temperature, position of equilibrium…
to endo products
more concentration of products, position of equilibrium…
goes to reactants
AND VICE VERSA
equilibrium expression
a simple relationship that links Kc to the equilibrium concentrations, or Kp to the equilibrium partial pressures, of reactants and products and the stoichiometric equation
equilibrium constant Kc
a constant which is calculated from the equilibrium expression for a reaction
mA + nB <=> pc + qD
(p,q,n,m = no. moles)
(A, B, C, D = concentration of reactant/product)
Kc = C^p * D^q / A^m * B^n
for Kc, which state is not included
solids
increasing temperature, Kc
decreases
pressure and concentration affect Kc
no
partial pressure
the pressure exerted by a particular gas A in a mixture of gases A, B, C
symbol p
pA / pA + pB + pC
Kp
A + 3B <=> 2C
Kp = C pressure ² / A pressure * B pressure³
mole fraction
the number of moles of a particular gas in a mixture of gases divided by the total number of moles of all the gases in the mixture, eg
mol R / mole R + mol S + mol T
Habers process
N2 + 3H2 <=> 2NH3
<>Hr = -92 kJ mol-1
.if ammonia is liquid = eq. to right
Contact process
2SO + O2 <=> 2SO3
<>Hr = -197kJ mol-1
neutralisation
the reaction of an acid with an alkali to form a salt and water
acid + alkali => salt + water
acid
proton (H+ ion) donor
eg. HCl, HNO3, H2SO4, CH3COOH
