15 - Chemical Equilibrium

Flashcards about chemical equilibrium concepts, equilibrium constants, and factors affecting equilibrium.

Dynamic Equilibrium

The condition where the rate of the forward reaction equals the rate of the reverse reaction, resulting in constant concentrations of products and reactants at a molecular level.

What Equilibrium is NOT

It isn't a complete stop of reaction; it's still occurring on a molecular level.

Equilibrium Constant (K)

The ratio at equilibrium of the concentrations of products raised to their stoichiometric coefficients divided by the concentrations of reactants raised to their stoichiometric coefficients.

What does a numerically large value of K indicate?

Numerically large values indicate the forward reaction is strongly favored, with relatively more products present.

What does the equilibrium constant depend on?

The valve of k

Changing the direction of the equilibrium reaction does what?

Inverting the constant.

Multiplying a reaction by a certain factor does what?

Raises K to that factor.

When adding 2+ individual reactions to obtain an overall equation, what happens to the corresponding constants?

They are multiplied to obtain the equilibrium constant for the overall reaction.

Kp

The equilibrium constant expressed in terms of partial pressures of reactants and products in the gas phase.

What is the relationship between Kp and Kc?

Kp = Kc(RT)^Δn, where Δn is the difference in moles of gas products and moles of gas reactants.

Heterogeneous Equilibrium

Pure solids and pure liquids do not appear in the equilibrium expression; their concentrations remain constant during the reaction.

ICE Table

A method used to determine the relative changes in concentrations of reactants and products to find equilibrium concentrations.

Finding 'x' using an ICE table

By substituting equilibrium concentrations into the Kc expression and solving for x.

Reaction Quotient (Q)

The reaction quotient (Q) is calculated using initial concentrations and compared to K to determine if the system is at equilibrium and, if not, which direction the reaction will shift.

If Q = K, then the…

System is already in equilibrium.

If Q < K, then the…

System needs more products/less reactants; reaction will go to the right to reach equilibrium.

Small - k approximation

If the K value is very small, very little NO2 decomposes and the size of the change is so small it can be neglected.

Le Chatelier's Principle

A chemical system, when taken out of equilibrium, will respond to the added stress by going in a certain direction to lessen the effect.

Effect of Adding a Species to a Chemical System

The reaction will shift in the direction that consumes the added species.

2 CO(g) = CO2(g) + C(s)

Adding or removing C(s) from this reaction at eq will not impact eq.

Effect on EQ Pressure Change

Has the same effect as changing its concentrations.

Adding an inert gas to N2(g) + 3 H2(g) = 2 NH3 (9)

Adding it won't affect equilibrium.

Changing Volume of Reaction container

The reaction goes in the direction that best utilizes the available space.