lect 11 Flashcards
what is the outline of this lecture?
-redox reactions
-nernst equation
-pE-pH diagrams
what is the cost of corrosion annually in the US?
over 1.1 trillion in 2016
-that is one of the largest expenditures we make, and it’s all going down the drain
-1998, 3.1% of GDP $276 billion. 2013, 3.1% of the 15.1 trillion US GDP, $500.7 billion
can corrosion present challenges in water security?
yea
-leaching from metal pipes
-can decrease the circumference of pipes
what are redox reactions?
reactions involving transfer of electrons
-oxidation of some species is balanced by reduction of another
what are some important redox processes in water?
where is the oxic and anoxic region in water?
what is basic redox?
what is electron activity and pE?
what is electron activity and pE conceptually?
conceptually the negative log of electron activity, pE expresses this activity over many orders of magnitude
when is electron activity 1?
if H+ activity is 1 and is in equilibrium with H2 at 1 atm (activity at 1), then activity of the electron is 1 and pE=0
what does a large positive pE mean? what about a large negative pE?
-large positive pE means oxidizing environments.. (and compound attracts electrons to itself; reduction)
-large negative pE means reducing environments (compound gives up electrons; oxidation)
when is G negative or positive? E? K?
what is the relationship between G E and K?
what are the non-standard conditions and the Nernst equation?
what are example of pE?
what is the example of nernst equation (examples of pE)?
what is the nernst equation and chemical equilibrium?
what are the limits of pE in water?
-when oxygen is produced at the pressure or 1.0 atm, this is oxidizing. limit of water: pE=20.75-pH
-when hydrogen gas is produced at the pressure of 1.0 atm, this is the reducing limit of water: pE=-pH
what is the graph of pH vs pE?
natural conditions are typically found int he central portion of the diagram
what is there was iron added to the pE-pH diagrams
what are the limits of pE in water?
what are the applications of pE-pH diagrams?
what is the template for use with pE-pH plots?
what are humic substances as natural reductants?
humic substances may function as reducing agents in natural water systems
-may be due to the quinone/hydroquinone group
