Solutions and Electrochemistry Flashcards
TRUE or FALSE: for gases, solubility decreases with increasing temperature.
TRUE
What does Henry’s Law state? What is the formula?
increasing pressure of a gas increases its solubility in a liquid (i.e. even if there is a lot of pressure, very little gas will dissolve)
C = kP (note: C = concentration, k = Henry’s constant, P = pressure)
Oxidation reaction entails a ___________ of electrons.
a) gain
b) loss
b) loss
Reduction reaction entails a ___________ of electrons.
a) gain
b) loss
a) gain
TRUE or FALSE: reduction reactions and oxidation reactions always occur together.
TRUE
If a species is oxidized, its oxidation number:
a) increases
b) decreases
a) increases
hint: LEO –> lose electrons
If a species is reduced, its oxidation number:
a) increases
b) decreases
b) decreases
hint: GER –> gain electrons
TRUE or FALSE: oxidizing agents are oxidized, and reducing agents are reduced.
FALSE: oxidizing agents are REDUCED, and reducing agents are OXIDIZED
What should the sum of all oxidation numbers for all atoms in a molecule equal to?
the overall charge of the molecule (see page 311 for rules for assigning oxidation numbers)
TRUE or FALSE: When calculating potential of a reaction, multiply the reduction or oxidation potential by the coefficients in the reaction.
FALSE –> do NOT multiply the potentials by the coefficients in the reaction (because reduction potentials are an INTENSIVE PROPERTY, independent of the amount of material present)
What is the oxidative potential for the H2 (g) –> 2H+ + 2e- half reaction? What is the name for this electrode?
E = 0 V; Standard Hydrogen Electrode (SHE)
When calculating the potential of the entire cell (anode and cathode), where the anode is associated with the standard hydrogen electrode (SHE) half-reaction, how do you calculate the answer for the potential of the entire cell/reaction?
E rxn = E reduction (at the cathode)
E rxn = E red + E ox, but E ox = 0 because of the SHE half-reaction
Positive E indicates a:
a) spontaneous redox reaction and positive delta G
b) nonspontaneous redox reaction and negative delta G
c) spontaneous redox reaction and negative delta G
d) nonspontaneous redox reaction and positive delta G
c) spontaneous redox reaction and negative delta G
The anode always undergoes a(n):
a) oxidation half-reaction
b) reduction half-reaction
a) oxidation half-reaction
hint: LEO –> anode has electrons to LOSE
The cathode always undergoes a(n):
a) oxidation half-reaction
b) reduction half-reaction
b) reduction half-reaction
hint: GER –> cathode (+) can GAIN electrons
What are the 3 main differences between galvanic/voltaic cells and electrolytic cells?
galvanic:
- spontaneous redox reaction
- cell produces energy and electric current
- anode is (-) and cathode is (+)
electrolytic:
- nonspontaneous redox reaction
- external energy required
- anode is (+) and cathode is (-)
Using the terms, anode reactant, anode product, cathode reactant, and cathode product, write the shorthand cell notation. What are 5 things to keep in mind when writing this notation?
anode reactant | anode product || cathode reactant | cathode product
- specify states (s, l, g)
- do NOT specify stoichiometric coefficients
- concentrations SOMETIMES specified
- single bar | = difference in state
- double bar || = salt bridge
Is the standard cell potential (E) for an electrolytic cell negative or positive?
NEGATIVE E for electrolytic cell because NONSPONTANEOUS rxn
What is Faraday’s First Law of Electrolysis?
mass of material produced at an electrode from electrolysis is directly PROPORTIONAL to the amount of electricity being transferred (Coulombs)
What is Faraday’s Second Law of Electrolysis?
equivalent amounts of electricity will produce different amounts of material proportional to the material’s weight
What is the formula used to calculate number of moles of electron (n), using Faradays law?
n = I x t x 1/F
note: n = number of moles of electrons, I = current, t = time, F = Faraday’s constant ~ 100,000 C/mol
What is the Nernst Equation?
E = E° - (RT/nF) ln(Q)
note: don’t need to use for calculation, but for predicting concentration cells???? …idk lol im confused what this is used for (pg. 326 chem cc)
a solution is a heterozygous mixture - true or false
false it is a homogenous mixture
what is the term referring to a solution where the solute particles are too small to be filtrated
colloids
what is the Tyndall effect
light scattering by the particles in a colloid
what are some examples of non polar solvents
hexane, diethyl ether and benzene
ionic compounds dissolve in ___ solvents
polar or nonpolar
polar
what is the formula for molality
moles of solute / solvent in kg
what is the formula for mass percentage
(mass of solute/mass of solvent ) x100%`
the vapor pressure of a liquid depends on _____
a) temp
b) volume
c) pressure
temperature
as the temperature of a liquid ____, the average kinetic energy _____ and the vapor pressure _____
fill in with increase or decrease
increases… increases…increases
at the normal boiling point, what is the pressure
1 atm (atmospheric)
bond breaking is _____ and bond forming is _____
fill in with exothermic or endothermic
endothermic… exothermic
what is Raoult’s law
????
rules for solubility
?????
