Notes taken during lecture
EXAM: 3 hours; 5 short answers, 28 M/C questions
half of exam is new material (untested)
other half is units 1 to 4
LECTURE 14
Slide No. Notes
electrochemistry deals with relationship between chemical
reactions and electricity
spontaneous reactions can produce electricity and electricity can
cause nonspontaneous reactions to occur
1Delta S is negative because entropy of gas greater than that of
liquids
Spontaneity ā calculate delta G
H and O gas both 0
Therefore spontaneous
Delta G = Delta H etc. formula
Both delta H and delta S are negative
Whenever both signs the same, some temperatures spontaneous
some not
Reaction becomes nonspontaneous at high temperatures
To calculate K for the reactionā¦
Delta G = RTInK
Q = 1/ (P of H2)squared times P of O2 = 1
Therefore K is greater than one for reaction to go to products
Therefore answer either E or D
To actually determine Kā¦
(1000J/kJ)(474kJ) = (8.314J/molK)(298K)InK
K = 1.44x10^83 therefore reaction goes to completion
Ans: E
To calculate temperature when reaction nonspontaneous
Calculate temperature when reaction switches from non
spontaneous to spontaneous
Delta G = Delta H ā T times delta S with delta G = 0
Delta H = 2mol(285.8kJ/mol) = 571.6kJ
Delta S = 2mol(699.9J/molK) ā 2mol(130.6J/molK) ā
1mol(205J/molK) = 326.4J/K
T = delta H/delta S = 1751 K
Reaction is nonspontaneous at temperatures above 1751K
2LEO: losing electrons is oxidation; GER: gaining electrons is
reduction
āOIL RIGā
overall reaction ā electrons cancel out

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Document Summary
Exam: 3 hours; 5 short answers, 28 m/c questions half of exam is new material (untested) other half is units 1 to 4. Notes electrochemistry deals with relationship between chemical reactions and electricity spontaneous reactions can produce electricity and electricity can cause nonspontaneous reactions to occur. Delta s is negative because entropy of gas greater than that of liquids. Delta g = delta h etc. formula. Both delta h and delta s are negative. Whenever both signs the same, some temperatures spontaneous some not. Q = 1/ (p of h2)squared times p of o2 = 1. Therefore k is greater than one for reaction to go to products. K = 1. 44x10^83 therefore reaction goes to completion. Calculate temperature when reaction switches from non (1000j/kj)(474kj) = (8. 314j/molk)(298k)ink spontaneous to spontaneous. Delta g = delta h t times delta s with delta g = 0. Delta s = 2mol(699. 9j/molk) 2mol(130. 6j/molk) . T = delta h/delta s = 1751 k.