13.3 Flashcards
what is the equation relating gibbs free energy to entropy
G = #H - T#Ssystem
how does gibbs free energy relate to the thermodynamic feasibility of a reaction
if #G is negative the reaction is thermodynamically feasible
if #G is positive the reaction is not thermodynamically feasible
if #G is 0 the reaction is in equilibrium
what is the equation for calculating the minimum temperature a reaction is thermodynamically feasible (#G = 0)
T = #H/ #Ssystem
what is the equation relating gibbs free energy and equilibrium constant
,#G = -RTlnK
K = e^(-#G/RT)
what occurs to the equilibrium when #G is negative and why
if #G is negative the exponent will be positive so the equilibrium constant will be greater than 1 so products are favored
what occurs to the equilibrium when #G is positive and why
if #G is positive the exponent will be negative so the equilibrium constant will be less than 1 so the reactants are favored
what is the equation given when the 2 gibbs energy equations are put together
lnK = -#H/RT + #Ssystem/R
use the equation for lnK to explain why increasing temperature means that the endothermic reaction is favored (if the forward reaction is exothermic)
if the forward reaction is exothermic then #H is negative and so -#H/RT is positive
if temperature increases then -#H/RT becomes less positive so lnK and hence K decreases
therefor equilibrium shifts to the left favoring the endothermic reaction
use the equation to explain why increasing temperature means that the endothermic reaction is favored (if the forward reaction is endothermic)
if the forward reaction is endothermic then #H is positive so -#H/RT is negative
if temperature increases then -#H/RT becomes less negative so lnK and hence K increases
therefor equilibrium shifts to the left favouring the exothermic reaction
eventhough gibbs value is negative the reaction may not occur why?
because the activation energy for the reaction is very high
if gibbs value is positive under standard conditions how can it be made feasible
change the conditions
if #solG is negative is the salt soluble
yes the salt is soluble
if #solG is positive is the salt soluble
no the solid salt is favored in the equilibrium
what is the equation for the relationship between #solG and Ksp
,#solG = -RTlnksp
what is the equation for the relationship between #solG and #solH and #Ssystem
solG = #solH -T#Ssystem
