Reactivity 2.3 — HL Flashcards
Reaction quotient
Ratio between the concentration of products and reactants for a reversible reaction not at equilibrium.
What does it mean if Q = K_c?
The system is at equilibrium, and no net change will occur in the concentrations of reactants and products.
How do you use Q to predict the direction of a reaction?
Compare Q to K_c: if Q < K_c, reaction goes forward; if Q > K_c, reaction goes in reverse; if Q = K_c, reaction is at equilibrium.
Define the equilibrium constant K_c.
K_c is a ratio of the equilibrium concentrations of the products raised to their stoichiometric coefficients to the equilibrium concentrations of the reactants raised to their stoichiometric coefficients, for a reaction at equilibrium.
What does the ICE table stand for, and what is its purpose?
ICE stands for Initial, Change, and Equilibrium. It’s used to organize and calculate the concentrations of reactants and products at the start, the change they undergo, and their concentrations at equilibrium.
What simplification can be made if K_c is very small?
If K_c is very small, the reaction barely proceeds towards the products, and the equilibrium concentrations of the reactants are approximately equal to their initial concentrations.
How do you determine the change in concentration in an ICE table?
The change in concentration is determined by the stoichiometry of the reaction and any given equilibrium concentrations. It is the amount consumed or produced as the system reaches equilibrium.
How is the equilibrium constant K_c affected by changes in concentration?
The value of K_c is not affected by changes in concentrations of reactants or products; it is a constant at a given temperature for a chemical reaction at equilibrium.
What is Gibbs Energy Change (ΔG)?
Gibbs Energy Change (ΔG) is the measure of the free energy change during a chemical reaction, indicating the spontaneity of the reaction.
What equation is used to calculate the Gibbs Energy Change (ΔG) from the equilibrium constant (K_c)?
ΔG° = -RT ln(K_c), where R is the universal gas constant (8.31 J K^-1 mol^-1), T is the temperature in Kelvin, and ln is the natural logarithm.
What does a negative ΔG value indicate about a chemical reaction?
A negative ΔG value indicates that the reaction is spontaneous under standard conditions.
How do you convert ΔG from joules per mole (J/mol) to kilojoules per mole (kJ/mol)?
Divide the ΔG value in joules per mole (J/mol) by 1000 to convert it to kilojoules per mole (kJ/mol).
How does the value of ΔG affect the equilibrium constant (K_c)?
If ΔG is negative, K_c > 1, indicating a reaction favoring products. If ΔG is positive, K_c < 1, indicating a reaction favoring reactants.
Why is temperature important when calculating ΔG from K_c?
Temperature affects the value of ΔG because it directly multiplies the natural logarithm of the equilibrium constant in the equation, influencing the spontaneity of the reaction.
