Section D Flashcards
Define thermodynamics
changes in the form of energy when a reaction occurs
Define equilibrium
reaction in which the reactants and products coexist
What is kept constant for the equilibrium constant?
Temperature, pressure, reaction
What is the difference between reaction quotient and equilibrium constant?
Kc describes a reaction that is at equilibrium, Q measures relative amounts of products (not at equilibrium)
What is the equation for reaction quotient?
[C]^c.[D]^d / [A]^a.[B]^b
Compounds in which state are omitted from the reaction quotient?
Pure liquids and solids are not included as they equal 1, aqueous and gaseous compounds are included in Q calc.
How do we calculate delta G using reaction quotient Q?
Delta G = Delta G0 + RT.lnQ
What is the case when Q > K?
Reaction favours reactants, delta G is positive, A + B
What is the case when Q = K?
System is at equilibrium, delta G = 0, delta G0 = -RT.lnK
At what point is the free energy change of a reaction zero?
When reaction is at equilibrium
What are some of the biological controlling functions of protons?
Controls: enzyme activity, synthesis of ATP, Oxygen transport, charge on proteins & lipids
What is the value of Kw?
10^-14 (at 25deg.)
What happens to the value of Kw when temperature increases?
Kw increases with temperature e.g. at 40deg. = 2.9 x 10^-14
What is the Arrhenius definition of acids and bases?
Acids increase the concentration of H3O+, bases increase the concentration fo OH-
What will the pKa be when equilibrium lies to the right?
Low pKa, strong acid,
Larger pKb = …
Stronger base - notice that it is pKb not pKa
At what point in a titration is the acid half neutralised?
when pKA = pH
What is another important doubly charged ion in biological systems?
Ca2+ is extremely important, most processes in cells involve calcium
What ion is highly regulate by buffering systems, controls charge balance on proteins, can be v. high conc. in certain organelles?
Protons (H3O+)
What is the Henderson-Hasselbach equation?
pH = pKa + log(A-/HA)
What are the 3 steps involved in making a buffer?
Choose acid/conjugate base with pkA ~ pH, calculate A-/HA ratio, check with pH meter
What is the equation for the solubility constant (Ksp)?
Ksp = [M+][X-]
What changes in the equation if the salt is not univalent?
If salt is MX2 for example, then equation for Kip would then = [M+][X-]^2
What happens when a sparingly soluble electrolyte is dissolved in a solution containing on of the ions?
Solubility decreases considerably,
Define voltage
Driving force of a reaction
Define current
quantity of electricity
What are alternate units of voltage?
1 volt = 1 joule/amp/sec
What are alternate units of current?
1 amp = 1 coulomb/sec
What is the conventional representation of a hydrogen electrode?
Pt | H2 (g, p), H+ (aq)
What reaction is a calomel electrode used in?
Pt | Hg, Hg2Cl2 | Cl- |, potential = 0.2767 at 25deg.
What is E0?
Standard redox potential at defined standard conditions
What is the equation for delta G0 involving E0?
Delta G0 = - n . F . E0
Derive an equation to find E0 using Kc
Use: Delta G0 = - n . F . E0 and Delta G0 = -RT.lnK to get: E0 = (RT/nF)lnK
What is the equation for E0 of a cell?
E0 cell = E0 right - E0 left
What is the Nernst equation?
E = E0 - (RT/nF).lnQ (E=measured EMF)
What is RT/F equal to at 25deg.?
0.02569V
In an ion selective electrode, what is electrode potential dependant on?
One specific ion in solution, develops a junction potential with internal solution also containing that ion
What ion can interfere with the pH electrode?
Na+
What is the conventional representation of a pH electrode?
H+ | H+,Na+ | Na+ | H+,Na+ | H+ | AgCl | Ag
What is the name for a cell which produces electricity?
Galvanic cell
What is the definition of an electrolytic cell?
Non-spontaneous reaction driven by an external current
What is 1 faraday equivalent to?
1 mole of electrons
How many coulombs are in 1 faraday?
96,485Coulombs in one faraday
