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Winter 2015 Exam ?'s
Terms in this set (16)
The slow evaporation of liquid water to water vapor at room temperature and pressure occurs spontaneously. The reason it is spontaneous is because
The INCREASE in entropy of the water more than offsets the ENDOTHERMIC phase change
A SPONTANEOUS redox reaction has
a POSITIVE value of Ecell and NEGATIVE value of ∆G
Calculate the cell potential, Ecell, for the redox reaction below @ 25C if the concentrations are as follows: [Ni2+] = 0.100M and [Fe+2] = 1.25M
1) Find value of Q with concentrations given then find n (@ of electron moles)
2) Plug into Ecell = Ecell - (0.0592logQ / n) equation
Process with _______ are SPONTANEOUS only at HIGH temperatures
Make negative and positive ∆S and ∆H "box"
answer = ∆H > 0 and ∆S > 0
Calculate the equilibrium concentration of Zn+3 (aq) in a solution that is initially 0.150M Zn(No3)2 and 0.800 NaCN. The formation constant for [Zn(CN)4] is Kf = 2.1E19.
1) set up Zn + 4CN --> Zn(CN)4^-2
2) set up ice table
3) 0.150 - X for reactants and 0.150 + X for products
4) plug into Kf
Indicate which of the following reactions would be expected to result in a POSITIVE ∆S
look at complexity, state phase, state changes for increase spontaneity
Butane is a fuel which can be burned to produce energy according to the reaction below. What is the maximum amount of energy you could derive from 10.0 g of C4H10? MM = 58.12 g/mol
Start with 10.0 gram, convert using 58.12 g (1 mole on top), 2 mole diagnally down, then 5496 kJ on top to end it
How do PEM fuel cells differ from traditional electrochemical cells (batteries)?
The supply of reactants in a fuel cell can be continuously replaced
Indicate which of the following is expected to have the SMALLEST standard molar entropy (S)?
look at state phase, then molar mass
For a redox reaction at standard conditions involving transfer of 3 moles of electrons, the standard free energy change is ∆G= -580 kJ. Using this information, calculate the standard cell potential, Ecell, for the reaction.
1) convert kJ to J
2) Use ∆G = -nFEcell equation
The Energizer Bunny in the television commercial "keeps going and going." What property of the battery (voltaic cell) is being featured in this commercial?
The larger quantities of reactants in the battery
The following titration curve is most likely associated with... (starts at 9pH ends at 3pH)
the titration of a weak base and strong acid titration
Which of the following represents the IONIZATION REACTION (i.e. with Ka) for a hydrated metal ion, M^2+, in aqueous solution?
M^2+(aq) + 2H20 <==> M(OH)^+ + H30+
remember 2H20 as a reactant
What mass of Cr metal would be deposited onto a metal object during electroplating of a Cr^3+(aq) solution for 45 minutes at a constant current of 2.5A?
Convert 45 minutes to 1 min to 60 seconds to 1 second to 2.5C
Use this value and convert using 9.649E4 C, 1 mole e- on top, 3 mole e- diagonally down, 1 mole on top, 1 mol diagonally down, molar mass of metal on top ending it
Which of the following is a correct statement of the Third Law of Thermodynamics?
The entropy of a PERFECT CRYSTAL at 0 K is zero
If a solution of BaCl2 is mixed with a solution of K3PO4, what condition would cause precipitation of Ba3(PO4)2(s) to occur?
set up 3Ba^+2 + 2PO4^-3 --> Ba3(PO4)2
answer = When [Ba^+2]^3[PO4^-3]^2 > Ksp
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