Equations 2 Flashcards
Average kinetic energy equation
KEavg = (3/2)(R)(T)
KEavg = average kinetic energy
R = gas constant (8.314)
NA = mol constant (or something)
T = temperature (K)
Graham’s law
r1/r2 = √(M2/M1)
or
T2/T1 = √(M2/M1)
r1 = rate of effusion/speed of gas 1
r2 = rate of effusion/speed of gas 2
M1 = molar mass of gas 1
M2 = molar mass of gas 2
T1 = time for gas 1 to diffuse
T2 = time for gas 2 to diffuse
The second equation is switched because T = amount delivered/time, and amount delivered cancels. Look at Diffusion and Effusion of Gases module for more information. Only works when amount delivered is equal.
Root mean square speed equation
urms = √(3RT/M)
urms = average root mean square speed
R = ideal gas constant, in this case, (always!) 8.314
T = temperature (K)
M = molar mass (in kg/mol)
van der Waals equation
[P + (an^2)/(V^2)]*(V - nb) = nRT
Instead of PV = nRT
a = strength of attraction between molecules of a particular gas
b = volume of the molecules of a particular gas
General equation for Kc to Kp
Kp = Kc(RT)^∆n
When ∆n = 0, Kp = Kc
Equilibrium constant for reverse reaction of Kc
1/Kc
How is Kc affected by multiplying coefficients?
Raise Kc to the power of whatever the coefficients were multiplied by. If Kc is reversed, the answer is still 1/Kc
Ex:
H2 + O –> H2O
Kc = 4
2H2 + 2O –> 2H2O
Kc = 4^2 = 16
1/2H2 + 1/2O –> 1/2H2O
Kc = 4^1/2 = 2
How is Kc affected when you add equilibria?
Multiply the Kc together
How are OH- and H3O+ (also can be called H+) concentrations related?
Kw = [OH-][H3O+]
Kw = 1x10^-14
How are Ka and Kb related?
Ka*Kb = Kw
Henderson-Hasselbalch equation
pH = pKa + log10 ([A–]/[HA])
[A-]: concentration of acid’s conjugate base
[HA]: concentration of the acid
Rewritten Henderson-Hasselbalch equation for pOH
pOH = pKb + log([BH]/[B])
[B+]: concentration of a base’s conjugate acid
[BOH]: concentration of the base
