Question 1

What does Le Châtelier's Principle state about systems at equilibrium?

Accepted Answer

Le Châtelier's Principle states that when a system at equilibrium is stressed by changes in concentration, temperature, or pressure, the system shifts to counteract the disturbance. This shift continues until a new equilibrium is reached. The principle explains how chemical systems naturally resist changes and maintain balance when external conditions are altered.

Question 2

How does increasing reactant concentration affect chemical equilibrium?

Accepted Answer

When the concentration of a reactant is increased, the equilibrium shifts toward the products to consume the excess reactant. This increases the rate of the forward reaction, producing more product until a new equilibrium is established. Understanding solutions and concentrations molarity molality helps predict these shifts accurately.

Question 3

Why is heat considered a reaction component in Le Châtelier's Principle?

Accepted Answer

In exothermic reactions, heat is released and acts as a product. In endothermic reactions, heat is absorbed and acts as a reactant. Since heat functions as either a product or reactant, adding or removing heat disturbs equilibrium, causing the system to shift and adjust to a new equilibrium state.

Question 4

What happens to equilibrium when a reactant is selectively removed from solution?

Accepted Answer

When a reactant is selectively removed through formation of an insoluble salt, its concentration decreases, and the equilibrium shifts left toward the reactants. This shift attempts to replace the removed reactant. Understanding the solubility rules of ionic compounds helps predict which ions precipitate and shift equilibrium.

Question 5

How do buffer solutions use Le Châtelier's Principle to resist pH change?

Accepted Answer

Buffer solutions contain a weak acid and its conjugate base in equilibrium. When strong acid is added, it increases hydrogen ion concentration, shifting the weak acid equilibrium left and reducing hydrogen ions until a new equilibrium forms. This buffering action maintains nearly constant pH despite acid addition.

Question 6

What does the color change in the iron thiocyanate reaction indicate about equilibrium shifts?

Accepted Answer

The iron thiocyanate complex is red, while reactants are colorless or yellow. When equilibrium shifts right toward products, the solution becomes more intensely red. When equilibrium shifts left toward reactants, the red color fades. These color changes provide visual evidence of how the system responds to concentration and temperature changes.

Question 7

How can Le Châtelier's Principle be applied to recover materials in industrial processes?

Accepted Answer

Le Châtelier's Principle guides material recovery by manipulating equilibrium through pH, temperature, or concentration changes. For example, ammonium recovery involves oxidizing water to separate ammonium ions, then shifting equilibrium at high pH to convert ammonium to volatile ammonia. This captured ammonia is then trapped in acidic medium, shifting equilibrium in the opposite direction.

Le Châtelier's Principle - Assessment Quiz