Chapter 10: Chemical Equilibrium

Question 1

dynamic equilibrium

Answer 1

-reached when the forward reaction rate is equal to the reverse reaction rate (concentrations of reactants and products remain constant… BUT NOT EQUAL)

Question 2

Keq

Answer 2

• can set forward and reverse reactions equal to each other and solve for k1/k2=Keq
• large Keq means that equilibrium occurs when there is a higher concentration of products than reactants
• small Keq means that equilibrium occurs when there is a lower concentration of products than reactants
• at equilibrium, the only factor that can change Keq is temperature (changing the concentration only changes the balance of the reaction)
• don’t include solids or liquids in Keq equation

Question 3

Le Chatelier’s Principle

Answer 3

• if any stress is placed on a system in equilibrium, then the the equilibrium is displaces in the direction that counteracts the stress
• concentration, volume (decrease the volume and the concentration of the gases increases, shift to remove the increase in partial pressure), adding gaseous reactants
• temperature changes (treat heat like a reactant or product… adding more shifts in opposite direction, same for taking away)

Question 4

Ka and Kb

Answer 4

-use interchangeably depending on which is in solution with water
-convert between using KaKb=Kw=1x10^-14
Kw also equals [OH-][H+]
-larger Ka means stronger acid

Question 5

pH and pOH

Answer 5

pH= -log[H+]
pOH= -log[OH-}
pH+pOH=14

Question 6

solubility constant, Ksp

Answer 6

• higher the constant, the more soluble (higher concentration of ions)
• solubility is equal to x in Ksp= [x]*[x]
• know how to use to predict the likelihood of a precipitate (if the Ksp is larger than what it should be, then it will precipitate because there is such a great concentration of ions)

Question 7

common ion effect

Answer 7

-when a reaction is in equilibrium, but there is an addition of ions already in solution, the result is that the reverse reaction will occur at a faster rate

Question 8

Second Law of Thermodynamics

Answer 8

-entropy of the universe increases for any spontaneous process (ΔS​universe=ΔS​system+ΔS​surroundings)
-positive means disorder increases, negative means decreases
-increases when number of moles increases or changes to more disordered state
​​-endothermic reactions can occur if surrounding entropy can overcome the negative of the system

Question 9

Gibbs Free Energy

Answer 9

ΔG=ΔH−TΔS

• if G is negative, then the reaction is spontaneous
• if G is positive, it is nonspontaneous