Unit 9 DNF Cards AP CHEM

Made by Alexie Dayrit

1. Thermodynamically favorable (spontaneous) reactions have a what sign for ΔG?

ALWAYS thermodynamically favorable: Negative (\Delta H) and Positive (\Delta S).

2a) Reactions with what signs for ΔH and ΔS are ALWAYS/NEVER thermodynamically favorable?

NEVER thermodynamically favorable: Positive (\Delta H) and Negative (\Delta S).

2b) If a reaction is “enthalpy driven & entropy driven”, what are signs of ΔH and ΔS?

(Delta H) is negative (exothermic) and (Delta S) is positive (increases disorder).

3. If a reaction increases/decreases the # of moles of gas, then the sign for ΔS is what?

Increase in moles of gas: (Delta S) is positive (+). Decrease in moles of gas:(Delta S) is negative (-)

4. If ΔG is (−)/(+), then Keq is greater than or less than 1?

(Delta G) is (-), K>1 & (Delta G) is (+), K<1

5. What are the most common units for ΔH and ΔS?

(Delta H)= kJ/mol; (Delta S)= J/mol*k

6. At equilibrium, what is the value of ΔG?

(Delta G) = 0

7. a) When using ΔGo = −RT lnK, the value for R is __________.

8,314 J/mol*k

7 b) If you use the value of 8.314 for R in the equation ΔGo = −RT lnK, then what are the units for ΔG?

J/mol

8. If a reaction is under kinetic control, what does that mean?

It means that the reaction is thermodynamically favorable but occurs at an extremely slow rate due to a high activation energy.

1a) When does hydrogen NOT have a +1 Oxidation # (besides when it is a pure element)?

Hydrogen has a -1 oxidation number when bonded to metals (ex. hydrides)

1b) When does oxygen NOT have a -2 oxidation number (besides when it is a pure element)?

 Oxygen has a -1 oxidation number in peroxides (ex. H2O2) and positive when bonded to Fluorine (F)

2. What does LEO goes GER stand for?

Lose Electrons Oxidation; Gain Electrons Reduction

3. Electrons in a battery flow in which direction?

Electrons flow from the anode to the cathode

4. In the salt bridge, which direction do the cations/anions ions flow?

Cations flow toward the Cathode; Anions flow toward the Anode.

5. While a battery is discharged, the mass of the cathode/anode increases or decreases?

The mass of the cathode increases (plating) and the mass of the anode decreases (dissolving).

6. If you reverse AND double a redox reaction, what happens to the magnitude AND sign of Eocell ?

If you reverse the reaction, the sign changes. If you double the reaction, the magnitude stays the same ( Eocell is an intensive property).

7. Given the reduction potentials for the half reactions, how do you calculate Eocell?

Ecell=Ereduction

8. The half-reaction with a more (+) / (-) EoRed is the reaction that takes place at which electrode?

More (+) Ered is the cathode & More (-) Ered is the anode.

9. When adding the two half reactions together, what is true about the # of electrons that are gained or lost?

The number of electrons gained must equal the number of electrons lost.

10. a) If ΔGo is (−) / (+) , then Eocell is positive or negative?

If (Delta G) is negative, Ecell is positive & If (Delta G) is positive, Ecell is negative.

b) ΔGo = −nFEo , what does ‘n’ refer to?

'(n)' refers to the moles of electrons transferred in the balanced redox equation.

11. If Q increases/decreases, then the voltage (Eocell) of the battery goes up or down?

If Q increases, voltage (Ecell) decreases & If Q decreases, voltage (Ecell) increases

12. Electroplating/Electrolysis Calculation Shortcut: grams of metal electroplated = _________?

g=(ItMM)/(n*F) (I= Amps, t=Sec, MM=molar mass, n=moles e