Molarity/LR Review
What are the units for molarity?
moles/Liters
Reversible Process
Processes that proceed in both the forward and reverse direction.
What are the units of Kc?
Unitless!
Write an expression for KC
2A + B ⇌ 2C + D
Kc = [C]2[D]/[A]2[B]
True or False:
Kc = KP
False
What is the molarity of 8.24g of NaCl dissolved in 672mL of water?
0.210 M
→ vs ⇌
A single arrow indicates all reactant molecules are converted to products at the end.
A double arrow indicates the reaction stops when only some of the reactant molecules have been converted into products.
How do you write an expression for an equilibrium constant to change a forward reaction to a backward reaction?
Take the inverse of the equation
Write the equilibrium constant expression (Kc) for the following equation:
N2(g) + 3H2(g) ⇌ 2NH3(g)
Kc = [NH3]2/[N2][H2]3
What is the equation to convert Kc to KP?
KP = Kc(RT)Δn
Calculate the number of moles of lithium in a 25mL 0.32M solution of lithium phosphide
0.024 mol Li+
Law of Mass Action
The relationship between the chemical equation and the concentrations of reactants and products.
What is the difference between Kc and KP?
Kc is used with concentrations, and KP is used with pressures
If Kc = 1.91 x 10-10, which of the following (if any) are true:
I. The reaction is product favored
II. The reaction is reactant favored
III. Equilibrium lies far to the right
IV. Equilibrium lies far to the left
II & IV
For the Haber process:
N2(g) + 3H2(g) ⇌ 2NH3(g)
Kc = 9.60 at 300 oC. Calculate KP.
KP = 4.34 x 10-3
How many grams of magnesium fluoride do you have to add to 64.3mL of solution to obtain a 0.42M of fluoride ions?
0.841g MgF2
Catalyst
A substance that increases the reaction rate without itself being consumed in the reaction. Does not affect either ΔH or the overall yield for a reaction. Lowers the total activation energy.
What happens when Kc >> 1?
Equilibrium will move to the right, for more products
For the following reaction, equilibrium is established by initially adding 0.10mol each of A and B to a 1L container, and Kc = 320. What is the concentration of C?
A + 2B ⇌ 2C
[C] = 0.566 M
For N2(g) + 3H2(g) ⇌ 2NH3(g), Kp = 4.34 x 10-3
What is the KP for the reverse reaction?
KP = 2.30 x 102
Potassium hydroxide reacts with sulfuric acid. There is 20mL of 1.6M potassium hydroxide. There is 32mL of 1.3M sulfuric acid. What is the max amount of salt produced, in grams?
2.79g K2SO4
Dynamic Equilibrium
The condition wherein the rates of the forward and reverse reactions are equal.
Chemical Equilibrium
When the rates of the forward and reverse reactions are equal and the concentrations of the reactants and products remain constant.
Once the following reaction comes to a stop, there is 0.24 mol of H2 present, 0.16 mol O2 present, and 0.43 mol H2O present in the 943mL solution. What is the equilibrium constant?
2H2(g) + O2(g) = 2H2O(g)
Kc = 18.8
Once the following reaction reaches equilibrium at 50 oC, there are 0.46 mol of N2, 0.19 mol of H2, and 0.96 mol of NH3 within 426mL of solution. What is the KP?
N2(g) + 3H2(g) ⇌ 2NH3(g)
KP = 0.0755