Notes Chemical equilibrium Flashcards
(77 cards)
What happens to chemical reactions before they are complete?
They often seem to stop but are actually reversible.
What is chemical equilibrium?
It is the state reached by a reaction mixture when the rates of the forward and reverse reactions have become equal.
In a reversible reaction, what do the original reactants form?
Products, which can react to give back the original reactants.
What does the graph of a chemical reaction approaching equilibrium show?
How the amounts of reactants and products change.
What is the ICE table used for in chemical equilibrium?
To organize the initial, change, and equilibrium amounts of substances.
What are the initial amounts of PCl5, PCl3, and Cl2 in the given equilibrium problem?
1.00 mol PCl5, 0 mol PCl3, 0 mol Cl2.
What is the equilibrium amount of PCl3 in the given example?
0.135 mol.
How do you calculate the moles of PCl5 at equilibrium if 0.135 mol of PCl3 is produced?
Moles PCl5 = 1.00 - 0.135 = 0.87 mol.
What is the equilibrium constant expression for a reaction?
It is obtained by multiplying the concentrations of products and dividing by the concentrations of reactants.
What is the equilibrium constant, Kc?
The value obtained for the Kc expression when equilibrium concentrations are substituted.
What is the Kc expression for the reaction 2H2(g) + CO(g) ⇌ CH3OH(g)?
Kc = [CH3OH] / ([H2]^2[CO]).
What does Kc use for its calculations?
Molar concentrations.
How do you find the value of Kc at equilibrium for the decomposition of CO2?
Use an ICE table to determine the changes in moles and substitute into the Kc expression.
What is the value of Kc for the reaction 2CO2(g) ⇌ 2CO(g) + O2(g) at equilibrium?
Kc = 0.82.
In a heterogeneous equilibrium, how are the concentrations of solids and pure liquids treated?
They are constant and incorporated into the value of Kc.
What happens to the Kc expression when a reaction is reversed?
The equilibrium constant expression is inverted.
What happens to the Kc expression when the reaction is doubled?
The equilibrium constant expression is squared.
Fill in the blank: The equilibrium constant expression for aA + bB ⇌ cC + dD is Kc = _______.
[C]^c[D]^d / [A]^a[B]^b.
True or False: The concentration of a solid or pure liquid is included in the Kc expression.
False.
What does the term ‘stoichiometric’ refer to in the context of chemical reactions?
The proportional relationship between reactants and products in a balanced chemical equation.
What is the general form of the equilibrium constant expression for the reaction aA(g) + bB(g) ⇌ cC(g) + dD(g)?
K = (C^c * D^d) / (A^a * B^b)
K represents the equilibrium constant, and the concentrations are raised to the power of their coefficients.
How are Kc and Kp related?
Kp = Kc * (RT)^(Δn)
Δn is the change in moles of gas, defined as (moles of gaseous products - moles of gaseous reactants).
What does it indicate when Kc is very large (>10^2)?
The equilibrium mixture is mostly products.
What does it indicate when Kc is very small (<10^-2)?
The equilibrium mixture is mostly reactants.