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15 Cards in this Set
- Front
- Back
- 3rd side (hint)
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chemical equilibrium physical and chemical
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physical - phase change H2O (l) -> H2O (g)
chemical - same phase different structure N2O4 (g) -> 2NO2 (g) |
physical liquid -> gas
chemical gas -> gas (changes) |
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law of mass action
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aA+bB <->cC+dD
K=((C)^c (D)^d) ÷ ((A)^a (B)^b) K = constant equilibrium |
reactants ÷ products = K
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Equilibrium will (favored)
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K = (C)^c (D)^d ÷ (A)^a (B)^b
Equilibrium will: K >> 1 lie to the right favor products reactant (small) & product (large) K<< 1 lie to the left favor reactants reactant (large) & product (small) |
if K is bigger than 1, it favors the right (products)
if K is smaller than 1, it favors the left (reactants) |
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Homogenous equilibrium pt.1
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-this applies to reactants in which all reacting species are in the same phase.
-general practice not to include units for the equilibrium constant. |
Kc = [NO2]^2 ÷ [N2O4]
Kp = P2[NO2] ÷ P[N2O4] |
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Homogeneous equilibrium pt.2
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if ∆n = 0, then Kp = Kc, in most cases Kc doesn't equal Kp
Kp = Kc(RT)^∆n ∆n = moles of gaseous products - moles of gaseous reactants = (c+d) - (a+b) R = 0.821 T = temp in °k liquids are not included, H2O is constant (is removed) Kp is only found if all are gases |
Kp = Kc(RT)^∆n
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Heterogeneous equilibrium
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-applies to reactions in which reactants and products are in different phases
CaCO3 (s) <-> CaO (s) + CO2 (g) Kc' = [CaO] [CO2] ÷ [CaCO3] (s) = constant Kc = [CO2] Kp = Pco2 |
this is when reactants and products are in different phases, solids and liquids don't count, only gases matter
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reciprocal of K
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N2O4 <-> 2NO2
K = [NO2]^2 ÷ [N2O4] = 4.63×10^-3 2NO2 <-> N2O4 K' = [N2O4] ÷ [NO2]^2 = 1÷K = 216 -when the equation for a reversible reaction is written in the opposite direction, the equilibrium constant becomes the reciprocal of the original equilibrium constant |
K' = 1÷K K = product ÷ reactant
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reaction quotient (Qc)
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-is calculated by substituting in the initial concentrations of the reactants and products into the equilibrium constant (Kc) expression. IF:
Qc < Kc system proceeds from left to right R->P Qc = Kc the system is at equilibrium R = P Qc > Kc system proceeds from the right to the left R<-P |
Qc<Kc left to right
Qc=Kc equal Qc>Kc right to left |
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Le Chatelier's Principle
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-if an external stress is applied to a system at equilibrium, the system adjusts in such a way that the stress is partially offset as the system reaches a new equilibrium position
-change in concentration N2 + 3H2 <-> 2NH3 equilibrium shifts left to offset stress if more NH3 is added |
change in concentration and stress will shift the equilibrium
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calculating equilibrium concentration pt.1
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-using an ICE Table, express equilibrium concentration in terms of initial concentrations and as single unknown x, which represents the change in concentration
-write the Kc in terms of Qc. knowing the values of the equilibrium constant , solve for x having solved for x, calculate the equilibrium concentration of reactants and products |
use the ICR Table, then use initial concentration and x to express equilibrium concentration. Then use Qc for Kc to solve for x. then calculate the equilibrium concentration
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Le Chatelier's Principle (adding a catalyst) pt.3 |
-Adding a catalyst - doesn't change K -doesn't shift the position of an equilibrium system -system will reach equilibrium sooner -catalyst lowers Ea for both forward & reverse reactions -catalyst doesn't change equilibrium constant or shift equilibrium |
No effect |
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Le Chatelier's Principle summary |
Change shift equilibrium constant Concentration yes no Pressure yes* no if moles are Volume yes* no equal Temperature yes* yes Catalyst no no |
Con. Yes no, pressure. Yes no, volume. Yes no, temperature. Yes yes, catalyst. No no |
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Chapter 15 Acids and Bases proton acceptor & donor |
A bronsted acid is a proton donor A bronsted base is a proton acceptor Conjugate base is gaining a proton Conjugate acid is losing a proton |
Who accepts, who donates, who's the conjugate base, who's the conjugate acid? |
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Acid - Base properties of water |
Autoionization of water |
Autoionization of water |
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The ion product of water |
The ion product constant (Kw) is the product of the molar concentration of H+ and OH- ions at a particular temperature - At 25°C Kw = [H+]×[OH-] = 1.0×10^-14 [H+] = [OH-] neutral [H+] > [OH-] acidic [H+] < [OH-] basic |
H = OH neutral H > OH acidic H < OH basic |
