equilibrium theory questions

What do chemists meanwhen they say that a reaction is reversible?

The reactants form products that react together to give the reactants back. They reach an equilibrium point where [ ] of reactants + products no longer change

4 things true about a system at equilibrium

• Concentrations of reactants + products are constant NOT THE SAME

• Forward + reverse reactions occur at equal rates

• State of dynamic balance, reactants continuously converting to products + vice cersa

• Gibbs free energy is at a minimum

What is meant by macroscopic properties?

• Macroscopic properties refer to the properties of a system that can be observed and measured without specifically focusing on individual particles or microscopic behavior. Examples include temperature, pressure, volume, and concentration.

How do the rates of the forward and reverse reaction compare at equilibrium?

At equilibrium, the rates of the forward and reverse reactions are equal. This does not mean that the reactions have stopped, but rather that the conversion of reactants to products and the conversion of products back to reactants occur at the same rate, resulting in no net change in the concentrations of reactants and products.

Do the forward and reverse reactions stop at equilibrium?

No, the forward and reverse reactions do not stop at equilibrium. At equilibrium, both reactions continue to occur, but they happen at the same rate, which means there's no net change in the concentrations of reactants and products. This constant activity is why it's referred to as dynamic equilibrium.

What can be said about the concentrations of all reactants and products at equilibrium?

At equilibrium, the concentrations of all reactants and products remain constant, but not necessarily equal. The rate of the forward reaction equals the rate of the reverse reaction, so there is no net change in concentration, even though reactions are still occurring dynamically. The specific concentrations depend on the equilibrium constant (K) for that reaction

Why is chemical equilibrium called dynamic equilibrium?

Chemical equilibrium is called dynamic equilibrium because, even though the concentrations of reactants and products remain constant over time, the reactions continue to occur. The forward and reverse reactions proceed at the same rate, resulting in no overall change in the system. This ongoing movement at the molecular level gives it the name "dynamic."

Why do systems tend toward minimum enthalpy?

• Systems favor lower energy (enthalpy) because it leads to greater stability. Reactions that release energy (exothermic) drive systems toward lower enthalpy.

Why do systems tend toward maximum entropy?

Systems naturally move toward greater disorder (entropy) because it's statistically more likely and thermodynamically favorable. More entropy means more possible arrangements of energy.

Why do gas particles have the most entropy?

gas particles have the most entropy because they are highly disordered and can move freely in all directions, leading to the greatest number of possible arrangements (microstates). This high level of randomness results in maximum entropy compared to liquids and solids.

When two tendencies—minimizing enthalpy and maximizing entropy—oppose each other..

the reaction will reach an equilibrium where both factors are balanced. The outcome depends on the specific conditions (temperature, pressure) and the balance between enthalpy and entropy.

Processes in which both the tendency toward minimum enthalpy and maximum entropy favor the products will

proceed spontaneously and go to completion, strongly favoring the formation of products.

Processes in which both the tendency toward minimum enthalpy and maximum entropy favor the reactants will

not occur spontaneously and will favor the reactants, meaning little to no product formation will occur.

Do systems always reach minimum enthalpy at equilibrium?

No, systems do not always reach minimum enthalpy at equilibrium. Equilibrium is achieved when the Gibbs free energy is minimized, not neceessarily the enthalpy. Changes in temperature, pressure, and composition can affect equilibrium without minimizing enthalpy.

Do systems always reach maximum entropy at equilibrium?

No, systems do not always reach maximum entropy at equilibrium. While equilibrium is associated with a state of maximum entropy under certain constraints, it depends on factors like energy conservation and external conditions. The system may reach a local maximum or a state of balance rather than the absolute maximum entropy.

As a reaction approaches equilibrium, the rate of the forward reaction _____, while the rate of the reverse reaction ______. Once equilibrium is reached, the rates become _____.

• decreases, increases, equal

State Le Chatelier’s Principle

Le Chatelier’s principle states that if a system at equilibrium is subjected to a change (or “stress”) in concentration, temperature, or pressure, the system will adjust in a way that counteracts that change and re-establishes equilibrium.