gen chem 2 final (chapters 19, 20, 21)

acid base buffer

a solution that resists changes in pH when a small amount of either strong acid or strong base is added

acid base titration curve

a plot of the pH of a solution of acid (or base) vs. the volume of base (or acid) added to the solution

buffer capacity

a measure of the ability of a buffer to resist a change in pH; related to the total concentrations and relative proportions of buffer components

buffer range

the pH range over which a buffer acts effectively

common ion effect

shift in the position of an ionic equilibrium away from an ion involved in the process that is caused by the addition or presence of that ion

complex ion

an ion consisting of a central metal ion covalently bonded to two or more anions or molecules called ligands

end point

the point in a titration at which the indicator changes color permanently

equivalence point

the point in a titration when the number of moles of the added species is stoichiometrically equivalent to the original number of moles of the other species

formation constant (K_f)

an equilibrium constant for the formation of a complex ion from the hydrated metal ion and ligands

Henderson[Hasselbalch equation

an equation for calculating the pH of a buffer system

Ligand

a molecule or an anion bonded to a central metal ion in a complex ion

selective precipitation

the process of separating ions through differences in the solubility of their compounds with a given precipitating ion

solubility product constant (K_sp)

an equilibrium constant for a slightly soluble ionic compound dissolving in water

adenosine triphosphate (ATP)

a high energy molecule that serves most commonly as a store and source of energy in organisms

coupling of reactions

the pairing of reactions of which one releases enough free energy for the other to occur

entropy (S)

a thermodynamic quantity related to the number of ways the energy of a system can be dispersed through the motions of its particles

free energy (G)

a thermodynamic quantity that is the difference between the system’s enthalpy and the product of the absolute temperature and the system’s entropy: G = H-TS

microstate

an instantaneous, quantized state of a system of particles throughout which the total energy of the system is dispersed

second law of thermodynamics

a law stating that a process occurs spontaneously in the direction that increases the entropy of the universe

spontaneous change

a change that occurs under specified conditions without an ongoing input of external energy

standard entropy of reaction (ΔG°rxn)

the entropy change that occurs when all components are in their standard states

standard free energy change (ΔG°)

the free energy change that occurs when all components of a system are in their standard states

standard free energy of formation (ΔGf°)

the standard free energy change that occurs when 1 mol of a compound is made from its elements with all components in their standard states

standard molar entropy (S°)

the entropy of 1 mol of a substance in its standard state

third law of thermodynamics

a law stating that the entropy of a perfect crystal is zero at 0K

ampere (A)

the SI unit of electric current

1 ampere of current results when 1 coulomb of charge flows through a conductor in 1 second

anode

the electrode at which oxidation occurs in an electrochemical cell

electrons are given up by the reducing agent and leave the cell at the anode

cathode

the electrode at which reduction occurs in an electrochemical cell

electrons enter the cell and are acquired by the oxidizing agent at the cathode

cell potential (E_cell) also electromotive force or cell voltage

the difference in electrical potential between the two electrodes of an electrochemical cell

coulomb (C)

the SI unit of electric charge

one coulomb is the charge of 6.242 × 10¹⁸ electrons

one electron possesses a charge of 1.602 × 10⁻¹⁹ C.

electrochemical cell

a system that incorporates a redox reaction to produce or use electrical energy

electrochemistry

the study of the relationship between chemical change and electrical work

electrode

the part of an electrochemical cell that conducts the electricity between the cell and the surroundings

Faraday constant (F)

the physical constant representing the change of 1 mol of electrons

F = 96,485 C/mol e⁻

half-cell

a portion of an electrochemical cell in which a half-reaction takes place

half-reaction method

a method of balancing redox reactions by treating the oxidation and reduction half-reactions separately

Nernst equation

an equation stating that the voltage of an electrochemical cell under any conditions depends on the standard cell voltage and the concentrations of the cell components

salt bridge

an inverted U tube containing a solution of nonreacting ions that connects the compartments of a voltaic cell and maintains neutrality by allowing ions to flow between compartments

standard cell potential (E°_cell)

the potential of a cell measured with all components in their standard states and no current flowing

standard electrode potential (E°_half-cell) also standard half-cell potential

the standard potential of a half-cell, with the half-reaction written as a reduction

standard hydrogen electrode (SHE)

a specially prepared platinum electrode immerse in 1M H⁺(aq) through which H₂ gas at 1 atm is bubbled

E°_half-cell is defined as 0V

volt (V)

the SI unit of electrical potential

1V = 1 J/C

voltaic/galvanic cell

an electrochemical cell that uses a spontaneous redox reaction to generate electrical energy