chemical equilibrium
What is the equilibrium constant?
Equilibrium constant (K) = [products]/[reactants]
Krxn = [C]c [D]d /[A]a [B]b
where the lowercase superscript letters denote stoichiometry coefficients and each capital letter stands for a chemical species. The symbol [A] stands for the concentration of A relative to its standard state (defined next). By definition, a reaction is favored whenever K > 1
From the following equation, state the K1:
HA<----> H+ + A-
K1= [H+] [A-] / [HA]
What is K controlled by?
Thermodynamics of a rxn
What is Le Chaterliers Principle?
Le Châtelier’s principle states that the direction in which the system proceeds back to equilibrium is such that the change is partially offset
What is pH?
List the rules when evaluating K
Rules:
Concentrations of solutes are expressed as moles per liter.
Concentrations of gases are expressed in bars.
Concentrations of pure solids, pure liquids, and solvents are omitted because they are unity i.e. assigned a value
Can you reverse that equation and state the new K1
H+ + A- <----> HA
K1' = [HA]/ [H+] [A-] = 1/K1
What is Enthalpy (H) and Entropy (S)
Enthalpy (H) is the amount of energy absorbed or released. Entropy (S) is the degree of disorder of a system
What is the solubility product?
The solubility product is the equilibrium constant for the reaction in which a solid salt dissolves to give its constituent ions in solution.
What is equation would you use to calculate pOH?
pH+ pOH =-lg(Kw) =14.00
The equilibrium constant for the reactionH2O <----> H+ + OH- is called Kw(=[H+] [OH-]) and has the value of 1.0 x10-14. Given that KNh3= 1.8 x10-5 for the reaction NH3(aq)+ H2O <-----> NH4+ + OH-, find K for the reaction NH4+ <----> NH3(aq) + H+.
H20 <----> H+ +OH- K=Kw
NH4+ + OH- <----> NH3(aq) + H20 K= 1/K NH3
NH4+ <------> H+ + NH3 (aq) k =Kw x 1/K Nh3 = 5.6x 10 -10
Complete this phrase:
Systems at constant temperature and pressure tend to have ----- (H) and ------ entropy (S
Systems at constant temperature and pressure tend to have lower enthalpy (H) and higher entropy (S
What is the common ion effect?
This application of Le Chatelier’s principle is called the common ion effect. A salt will be less soluble if one of its constituent ions is already present in the solution.
What are strong acid and bases?
What are weak acids and bases?
Strong acids and bases completely dissociate in water.
Weak acids and bases dissociate partially in solution
What is Gibbs Free Energy?
ΔG = ΔH - T ΔS
What is the inert salt effect?
Adding an “inert” salt (KNO3) to a sparingly soluble salt (CaSO4) increases the solubility of the sparingly soluble salt. “Inert” means that KNO3 has no chemical reaction with CaSO4. When we add salt to a solution, we say that the ionic strength of the solution increases.
What is pH of a 0.1M HCl and NaOH solution?
Find pOH.
[H+] = 0.1 M; pH = -log (0.1) = 1.00
[OH-] = 0.1 M; pOH = 1.00
pH = 14.00 – pOH = 14.00 – 1.00 = 13.00
What is ionic strength?
Ionic strength, is a measure of the total concentration of ions in solution. The more highly charged an ion, the more it is counted