Ch14: Kinetics
What is the overall order for the following rate law?
Rate = k[A][B]2
3rd order!
What is Kp used for? What about Kc?
Kp is the equilibrium constant when pressure is involved. Kc is the equilibrium constant when concentration is involved.
What are our common STRONG ACIDS?
HCl (aq), HBr (aq), HNO3 (aq), H2SO4 (aq), HClO4(aq), HCLO3 (aq), HI (aq)
*must contain at least one H+
TRUE/FALSE
At the equivalence pt. of a strong acid/strong base titration at 25 degrees Celsius, the pH is always 7.00
TRUE
What is the first law of thermodynamics?
Energy cannot be created or destroyed, only converted from one form to another.
Write the rate expression for the following reaction:
2A + 3B -> C
Rate = -(1/2)(d[A]/dt) = -(1/3)(d[B]/dt) = +(d[C]/dt)
What is the difference between K and Q?
K is at equilibrium
Q is at any other point than equilibrium
TRUE/FALSE:
Strong bases undergo complete dissociation in water.
NaOH(aq) > Na+(aq) + OH-(aq)
TRUE!
Same goes for strong acids!
TRUE/FALSE
Buffers are a weak acid or weak base and its conjugate weak base or weak acid
TRUE
In your own words, what is the difference between Entropy and Enthalpy. Give examples of each!
Enthalpy (ΔH): Sum of a systems internal energy and product of pressure and volume.
- when you heat up pizza rolls(system) in the microwave, energy is transferred into them in the form of heat.
Entropy (ΔS): Related to the # of possible ways we can order a collection of things.
- perfume spreading through a room
- related to micro states
What is the integrated rate law equation for a first order reaction?
ln([At]/[A0]) = -kt
What equation relates Gibbs Free Energy and equilibrium and what does each part mean?
dG = dGo + RTlnQ
dG is Gibbs Free Energy; dGo is Gibbs Free Energy at standard conditions; R is the gas law constant; T is temperature; Q is the reaction quotient
For the following reaction, label the acids, bases and the conjugates.
NH3(aq) + H2O(l) -> NH4+(aq) + OH-(aq)
Acids: H2O, NH4+
Bases: NH3, OH-
Conjugates: NH3(b) & NH4+(a); H2O(a) & OH-(b)
Fill in the phrase with either "lower" or "higher"
A lower Ksp = ________ Solubility
A higher Ksp = ________ Solubility
A lower Ksp = lower Solubility
A higher Ksp = higher Solubility
Which represents a spontaneous process:
a) -ΔS
b) -ΔH
c) -ΔG
-ΔG
Remember:
ΔG < 0 spontaneous
ΔG > 0 non-spontaneous
ΔG = 0 equilibrium
What are the five factors that alter the rate of a reaction?
Particle size of solids, nature of reactants, concentration of reactants, temperature, and presence of a catalyst.
What do each of these comparisons mean?
Q=K ; Q>K ; Q<K
Q=K: Reaction is at equilibrium
Q>K: Needs more reactants, reaction goes backward
Q<K: Needs more products, reaction goes forward
Write all reactions for H3PO4 until it is fully deprotonated. Assume it reacts with H2O. Ignore phases.
H3PO4 + H2O -> H2PO4- + H3O+
H2PO4- + H2O -> HPO42- + H3O+
HPO42- + H2O -> PO43- + H3O+
DOUBLE JEOPARDY!
Will a precipitate form when Q=1.94 x 10-28
and Ksp(Cr(OH)3)= 3.00 x 10-29
Cr(OH)3 (s) Precipitate forms
This can be done w/o calculations.
Predict the sign of ΔS for the following reactoin:
NaCl (s) + H2O (l)> NaCl (aq) + H2 (g)
ΔS > 0 (positive)
What is the value of the activation energy for the decomposition of HI?
2HI(g) -> H2(g) + I2(g)
k1 = 8.15 x 10-8 M-1s-1 ; T1 = 655 K
k2 = 1.39 x 10-6 M-1s-1 ; T2 = 705 K
Use 2-point Arrhenius:
ln(k1/k2) = (Ea/R)[(1/T2)-(1/T1)]
Ea = 218 kJ/mol
Find Kc for the following set of half reactions:
A + B -> C Ka = 0.80
D -> 2C Ka = 2.5
Full reaction is: 2A + 2B -> D
Kc = 0.26
Find the concentration of HA at equilibrium for the following reaction if you start with 0.20 M HA and the Ka of HA is 6.3 x 10-6. Assume 5% rule is valid.
HA(aq) + H2O(l) -> A-(aq) + H3O+(aq)
Use an ICE table!
x = 0.0011
[HA]eq = 0.199 M
Calculate the pH of the solution when you titrate 250.0mL of 0.350 of NH3(aq) with 75ml of a 0.550 M HCl(aq). Kb(NH3)=1.8x10-5
Calculate the ΔSsurrounding for the following balanced rx at 35 degrees Celsius give ΔH⁰rx = 217.8(kJ)
2HgO (s)> 2Hg(s) + O2(g)
Using: ΔSsurr = -ΔH⁰rx IN J / Temp
-707.0 J/K