FINAL Chapter 5/18/19 Flashcards
(19 cards)
Define state function and give an example
Analogous to conservative force, path independent (inital and final states of system not path taken to get there)
Property whose value dpeneds only on the state of the system, not on how it reached that state
Energy, enthalpy and entropy are examples
For entropy and enthalpy, what is thermodynamically favourable?
Exothermic because it increases entropy, and positive entropy to maximize number of accessible microstates
For change in enthalpy and entropy what is the equation?
Product-reactant
What increases entropy of system?
Solid to gas, greater number of molecules/ions or increase in temperature
For the equation
∆G = ∆H - T∆S
what signs of H and S make spontaneous and nonspontaneous
Spontaneous when ∆G is negative
Draw graph with ∆H representing the x axis and ∆S representing the y axis
Top left is spont, bottom right is not
Bottom left is spont at low temperatures and top right is spont at high temperatures
What electrode does reduction occur at and what electrode does oxidation occur at?
Reduction - cathode
Oxidtation - anode
What is the equation for cell potenntial?
Cathode - anode
In voltaic cell and electrolytic which anode is positive and which is negative
Voltaic
Anode (-) and cathode (+)
Electrolytic
Anode (+) and cathode (-)
With chart how can you know if reaction is spontaneous
If OA is above RA
reduction above oxidation
What is a concentration cell?
What do you have to remember when solving these problems
Voltaic cell for which same anode and cathode material but different ion [ ] so current is produced
E cell standard is equal to 0
CHAPTER 5/18
When boiling a pot of water, some of the energy is used to increase the temperature of the water, while
some of the energy is required to convert liquid water into water vapour. From the total energy required
to convert 100 mL of liquid water at 25 °C to water vapour at 100 °C, calculate what percent is used to
increase the temperature of the water.
Specific heat capacity of water = 4.184 J/g·K
𝑯𝟐𝑶(𝒍) → 𝑯𝟐𝑶(𝒈) ΔH = 2257 J/g
For temperature change you use the equation
q = mc∆t
for phase changes it’s simply
q = m∆h
q total = mch + mct
Now calcualte both q values and then do a percentage
so temp change/temp change + phase change* 100%
Enthalpy change of formation of O2
0
How to balance an equation as such where
IO3- = I2
It becomes
2IO3- = I2
and you go from +10 to 0
2IO3- + 10e = I2
What is unit of ∆𝐺°? and R
It should be J in all equations but for
∆𝐺° = ∆H-T∆S, ∆H should be converted to J,
entropy measured in J
8.314 in J and 0.008314 in kJ
Define state
The complete set of properties that define a system
Define the 1st and 2nd law of thermodynamics
1st - total energy of an isolated system is constant as matter can not be created nor destroyed
2nd - in any spontaneous process the entropy of the universe increases
Define pv work
work is the transfer of energy that is based on change in volume at constant pressure and is denoted by W = PΔV
The more positive Ecell value is always the OA or the RA?
OA
What materials are needed to build a cell with the following reaction
5Cu2+ + 24H+ + 4IO3- = 5CU + I2 + 6H20
Copper is anode oxidized and iodate is cathode reduced
Anode:
Copper electrode and the solution would be 1M copper Cu2+ ions from CuSo4
Cathode:
Platnium or graphite (C) electrode and the solution would contain 1M KIO3 ions to provide the iodate ions along with the acidic conditions as seen in teh equation usally by 1M of H2SO4
