What is chemical equilibrium?

Chemical equilibrium is the state in a reversible reaction where the forward and reverse reactions occur at equal rates, leading to no net change in the concentration of reactants and products.

What does the double arrow (⇌) in a chemical equation indicate?

It represents a reversible reaction where the reactants are forming products at the same rate as the products are converting back into reactants.

What is dynamic equilibrium?

Dynamic equilibrium occurs when the forward and reverse reactions continue to occur but at equal rates, keeping the concentrations of reactants and products constant.

What is an example of equilibrium in a physical process?

The equilibrium between liquid water and its vapor:
H₂O(l) ⇌ H₂O(g)
where the rate of evaporation equals the rate of condensation.

What is Henry’s Law for gas-liquid equilibrium?

Henry’s Law states that the solubility of a gas in a liquid is directly proportional to its partial pressure above the liquid:
C = kP
where C is the solubility, k is the Henry’s law constant, and P is the pressure.

What happens to the solubility of a gas in a liquid when pressure increases?

The solubility of the gas increases, as predicted by Henry’s Law.

What is the Law of Chemical Equilibrium?

The equilibrium constant (Kc) is defined as the ratio of the product of equilibrium concentrations of products raised to their stoichiometric coefficients to the product of equilibrium concentrations of reactants raised to their stoichiometric coefficients:

Kc = [C]^c[D]^d / [A]^a[B]^b

for a reaction of the form:

aA + bB ⇌ cC + dD

What is the relationship between Kc and Kp?

For gaseous reactions:

Kp = Kc(RT)Δn

where Δn is the difference in moles of gaseous products and reactants.

What does Le Chatelier’s Principle state?

If an external stress (change in concentration, pressure, or temperature) is applied to a system at equilibrium, the system shifts in a direction that minimizes the stress.

What happens when you increase the concentration of a reactant in equilibrium?

The system shifts toward the products to consume the added reactant.

What happens when pressure is increased in a gaseous equilibrium?

The equilibrium shifts in the direction of fewer moles of gas to reduce pressure.

What is the effect of a catalyst on equilibrium?

A catalyst does not change the equilibrium position but helps the system reach equilibrium faster by increasing the rate of both forward and reverse reactions.

What is the reaction quotient (Qc)?

It has the same expression as the equilibrium constant but is calculated using initial concentrations instead of equilibrium concentrations.

How can Qc predict the direction of a reaction?

• If Qc < Kc: The reaction shifts forward (toward products).
• If Qc > Kc: The reaction shifts backward (toward reactants).
• If Qc = Kc: The system is at equilibrium.

What is the relationship between equilibrium constant (K) and Gibbs free energy (ΔG)?

ΔG = ΔG⁰ + RT ln Q

At equilibrium, ΔG = 0,
so:

ΔG⁰ = -RT ln K

What does the value of K indicate about reaction spontaneity?

• If K > 1, the reaction is spontaneous in the forward direction (ΔG⁰ < 0).
• If K < 1, the reaction is non-spontaneous in the forward direction (ΔG⁰ > 0).
• If K = 1, the system is at equilibrium (ΔG⁰ = 0).

What are the Arrhenius definitions of acids and bases?

• Acid: Increases H⁺ concentration in water.
• Base: Increases OH⁻ concentration in water.

What is the pH formula?

pH = -log [H⁺]

What is the relationship between pH and pOH?

pH + pOH = 14

What is the ionic product of water (Kw)?

Kw = [H⁺][OH⁻] = 1.0 × 10^-14 at 25°C

What is the Henderson-Hasselbalch equation?

pH = pKa + log ([A⁻] / [HA])

where pKa = -log Ka.

What is the solubility product constant (Ksp)?

Ksp = [Mm+]m [Xn-]n 
for a salt MnXm dissolving as:
MnXm ⇌ nMm+ + mXn-

What is the common ion effect?

The reduction in solubility of a salt when a common ion is already present in the solution.

What is the Haber Process for ammonia synthesis?

N₂(g) + 3H₂(g) ⇌ 2NH₃(g)
Conditions favoring forward reaction:

• Low temperature (but not too low)
• High pressure
• Iron catalyst

What is the Contact Process for sulfuric acid production?

2SO₂(g) + O₂(g) ⇌ 2SO₃(g)
Conditions favoring forward reaction:

• Vanadium(V) oxide catalyst (V₂O₅)
• Moderate temperature
• High pressure