Equilibrium Flashcards
What is chemical equilibrium?
It’s when the concentrations of reactants and products no longer change because the forward and reverse reactions occur at the same rate.
What does Le Chatelier’s principle state?
When a system at equilibrium is subjected to stress, it will shift in a direction that attempts to counteract the stress.
If the concentration of a substance is increased in a system at equilibrium, which direction does the equilibrium shift?
The equilibrium shifts away from the substance whose concentration was increased.
How does an increase in pressure affect a system at equilibrium?
The equilibrium shifts toward the side with fewer moles of gas.
What happens when the temperature of a system at equilibrium is increased?
The equilibrium shifts to consume the added energy (favoring the endothermic reaction).
What is the effect of adding a catalyst to an equilibrium system?
No shift occurs; a catalyst only speeds up the reaction to reach equilibrium faster.
What happens if the volume of a gas system at equilibrium is increased?
The equilibrium shifts toward the side with more moles of gas.
What does the equilibrium constant (Ke) tell you about the reaction?
Answer: If Ke > 1, products are favored; if Ke < 1, reactants are favored; if Ke = 1, products and reactants are present in equal concentrations at equilibrium.
What is an acid according to the Bronsted-Lowry theory?
An acid is a substance that donates protons (H+ ions).
What is a base according to the Bronsted-Lowry theory?
A base is a substance that accepts protons (H+ ions).
What is the conjugate base of an acid?
The conjugate base is the particle that remains after an acid donates a proton.
What defines a strong acid or base?
A strong acid or base completely dissociates in water into its ions.
What does the Ka value tell you about an acid’s strength?
The smaller the Ka, the weaker the acid.
What defines a weak acid or base?
A weak acid or base only partially dissociates in water, meaning the concentration of hydronium ions is less than that of the acid or base.
What is the difference between a weak acid and its conjugate base?
A weak acid will donate a proton, while its conjugate base can accept that proton.
What is a buffer?
A buffer resists changes in pH when small amounts of acid or base are added.
What are the components of a buffer solution?
A buffer solution is made of a weak acid and its conjugate base (or a weak base and its conjugate acid) in roughly equal concentrations.
What is buffer capacity?
Buffer capacity is the amount of acid or base a buffer can absorb before there is a significant change in pH.
What is the purpose of a titration?
The purpose of a titration is to determine the concentration of an unknown solution by reacting it with a solution of known concentration.
What is the equivalence point in a titration?
The equivalence point is when the number of moles of acid equals the number of moles of base in a solution.
What is the pH at the equivalence point for a strong acid-strong base titration?
The pH is 7 at the equivalence point.
How do you choose an indicator for a titration?
The indicator should change color at a pH close to the equivalence point, which can be determined by examining the titration curve.
What does the solubility product constant (Ksp) represent?
Ksp represents the equilibrium constant for the dissolution of a solid into its ions in a solution.
What happens when Q = Ksp?
The solution is saturated.
What happens when Q > Ksp?
A precipitate forms.
What happens when Q < Ksp?
No precipitate forms, and the solution is unsaturated.
