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OAT General Chem
Electrochemistry, Chemical Kinetics, Thermochemistry, and Chemical Equilibria
| Term | Definition |
|---|---|
| electrochemical reactions | spontaneous reactions that produce electrical energy and nonspontaneous reactions that use electrical energy to produce a chemical change |
| electrochemical cells | contained systems in which a redox reaction occurs wither to provide electrical energy or to use electrical energy |
| electrodes | electrical conductors where oxidation and reduction occur |
| anode | where oxidation occurs |
| cathode | where reduction occurs |
| galvanic cells | - has a negative delta G and a spontaneous reaction - supply energy is harnessed by placing the oxidation and reduction half-reactions |
| electrolytic cell | - has a positive delta G and a nonspontaneous reaction - electrical energy is required to induce reaction |
| faraday constant | equivalent to the amount of charge contained in one mole of electrons 1 F = 96,487 C/mol |
| reduction potential | the tendency of a species to aquire electrons and be reduced measured in volts (V) |
| standard hydrogen electron | given a potential of 0 volts and is based on the half-reaction 2 H+ (aq) + 2e- --> H2 (g) |
| standard reduction potential (E°) | measured under standard conditions (25°C) a higher E° means a greaater tendency for reduction to occur a lower E° means a greater tendency for oxidation |
| standard electromotive force (E° cell) | the difference in potentials between two half cells E°cell = E°red + E°ox |
| Gibbs free energy equation | ^G = -nFEcell (if the faraday is expressed in coulombs (J/V) ^G must be expressed in J not kJ) |
| Nernst equation | Ecell = E°cell - (RT/nF)(ln Q) (Q = reaction quotient ([C]^c [D]^d /[A]^a [B]^b)) |
| mechanism | a chemical reaction that is the actual series of steps through which it occurs |
| intermediate | two steps add up to the overall (net) reaction A2B which does bot appear in the overall reaction because it is neither a reactant nor a product |
| rate-determining step | - the slowest step in a proposed mechanism - the overall reaction cannot proceed faster than that step |
| reaction rate | the change of concentration of reactant or finished product reactants --> products |
| rate | rate = - ^[A]/^t + -^[B]/^t = ^[C]/^t |
| rate law | rate = k[A]^x[B]^y |
| rate constant | a constant of propotionality between the chemical reaction rate and the concentation of the reactants |
| orders of reaction | the exponents x and y x is the order with respect to A y is the order with respect to B the exponents are equal to the stoichiometric coefficients of the rate-determining step |
| overall order of a reaction | the sum of the exponents x + y |
| zero-order reactions | has a constant rate which is independent of the reactants' concentrations rate = k (where k has units of M*s^-1) |
| first-order reactions | - order = 1 - has a rate proportional to the concentration of one reactant rate = k[A] or rate = k[B] |
| second-order reactions | - order = 2 - has a rate proportional to the product of the concentration of two reactants or the square of the concentration of a single reactant - rate = k[A]^2, rate = k[B]^2, or rate = k[A][B] |
| higher-order reactions | - has an order greater than 2 -more possible combinations |
| mixed-order reactions | - has a fractional order - rate = k[A]^1/3 |
| collision theory of chemical kinetics | state that the rate of a reaction is proportional to the number od collisions per second between the reacting molecules |
| effective collision | - one that leads to the formation of products - occurs only if the molecules collide with the correct orientation and sufficient force to break existing bonds and form new ones |
| activation energy | the minimum energy of collision necessary for the reaction to take place |
| transition state | - when molecules collide with sufficient energy and in correct orientation - old bonds are weakened and the new bonds are beginning to form |
| reaction coordinate | a measure of the extent to which the reaction has progressed from reactants to products |
| activiated complex | has greater energy than either the reactants or products -either dissociate into the products or revert to reactants without any additional energy input |
| potential energy diagram | illustrates the relationship between the activation energy, the heats of reaction, and the potential energy of the system before and after the reaction |
| enthalpy change | the difference between the potential energy of the products and the potential energy of the reactants |
Created by:
Jalisa.bland
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