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
is calcium nitrate soluble in water and why
it is soluble because both the enthalpy and entropy terms are favorable
is magnesium sulfate soluble in water and why
it is soluble because the favorable enthalpy term outweighs the unfavorable entropy term
is sodium nitrate soluble in water and why
it is soluble because the unfavorable enthalpy term is outweighed by the favorable entropy term
is silver chloride soluble in water and why
it is only sparingly soluble because the unfavorable enthalpy term outweighs the favorable entropy term
is barium sulfate soluble in water and why
it is sparingly soluble because both the enthalpy and the entropy are unfavorable
is calcium carbonate soluble in water and why
it is sparingly soluble because the favorable enthalpy term is outweighed by the unfavorable entropy
how can you prove HCl is a strong acid
dissociation of HCl in water has a negative #H value (favorable) and a negative #S value (unfavorable) this therefor makes #G negative (favorable) and allows us to calculate #G and then calculate k which matches that of a strong acid, HCl has favorable enthalpy term which out ways the unfavorable entropy term
why is HF a weak acid
the hydrogen bonds is strong and therefor it dissociates less
why is acid strength of chloroethanoic acid greater than ethanoic acid
the electron withdrawing chlorine atom polarises the OH bond in the carboxylic acid making it easier to ionize
