-
to be spontaneous the change in S must be
Greater than 0
-
Things that can increase entropy are:
- 1. increase in temp
- 2. volume increase
- 3. moving particle increase
-
Processes that can increase entropy
- 1. solid/liquid -> gas
- 2. solid -> liquid
- 3. gas molecule increase
-
properties of the system that depend only on its present state
state functions
-
change H +
change S -
- change G +
- always nonspontaneous
-
change H -
change S +
- change G -
- always sponstaneous
-
change H -
change S -
spontaneous @ low temps
-
change H +
change S +
spontaneous @ high temps
-
what is a voltaic or gavanic cell?
* an electrochemical cell in which a spontaneous rxn generates an electric current
* Has 2 half-cells that are electrically connected
-
What is the purpose of a salt bridge?
to allow the flow of ions while preventing the mixing of the different solutions that would allow direction rxn of the cell reactants
-
which "ode" is oxidation?
anode
-
which "ode" is reduction?
cathode
-
directions of the "odes"
- anode gives up electrons
- flows to cathode
-
Which "ode" is + and which is -?
-
Rules for describing voltaic cell short hand style:
- 1. anode(oxidation) on left, cathode(reduction) on right
- 2. vertical line to indicate phase boundary (solid and solution)
- 3. 2 vertical lines for salt bridge
-
-
If E is positive:
rxn is spontaneous
-
equation for standar E:
E(cathode)-E(anode)=
-
Which half-rxn should you flip signs on?
cally said the most negative one
-
what is coulombs x volts?
Joules
-
What is coulomb?
the amount of electric charge transported by a steady current @ 1 atm
-
When is the Nernst equation used?
to calculate cell potentials at non-standard states
-
Explain Electroplating
- * a plating process in which metal ions in a solution are moved by an electric field to coat an electrode.
- * electrical current reduces cations of a desired material from a solution and coats a conductive object with a thin layer of material, such as a metal.
- * Used for: abrasion and wear resistance, corrosion protection, lubricity, aesthetic qualities
-
What is corrosion?
- * the gradual destruction of material, usually metal, by chemical reaction with its environment
- * electrochemical oxidation of metals in reaction with an oxidant such as oxygen.
- *Rusting, the formation of iron oxides
-
Define electrolysis
a method of using a direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction
|
|
