Concentration Changes
Adding more of a reactant causes the equilibrium to shift in which direction?
Towards the products
Decreasing the volume of a gas-phase system shifts equilibrium in which direction?
Towards the side with fewer moles of gas.
What type of reaction has higher Kc at higher temperatures?
Endothermic reactions
What is Le Chatelier's Principle?
A system at equilibrium shifts to relive any applied stress.
Removing a product from a system at equilibrium causes the reaction to shift in which direction?
Towards the product.
A gas-phase reaction has an equal number of moles of gas on both sides. What happens to the equilibrium position if the volume is changed?
No shift occurs.
For an exothermic reaction, increasing temperature shifts equilibrium in which direction?
Towards reactants.
Which three main factors can disturb equilibrium?
Concentration, pressure/volume, and temperature changes
If extra NH3 is added to the equilibrium N2 + 3 H2 -> 2 NH3, how will the system respond?
Shifts left, more reactants are made.
What happens if you add an inert gas like argon to an equilibrium mixture?
No change.
In Le Chatelier terms, how can "heat" be treated in an exothermic reaction?
As a product.
When a stress is applied, what happens to Qc relative to Kc?
They become unequal.
Why doesn't adding or removing a pure solid or liquid affect equilibrium?
Solids and liquids don't appear in the Kc expression, Qc = Kc
When the volume of a reaction vessel doubles, what happens to the concentrations of all gaseous species?
Concentration decreases by half.
If the reaction is endothermic, does Kc increase or decrease with increase in temperature?
Kc increases.
If a stress is applied to a system and the equilibrium shifts to reestablish balance, what remains unchanged: Qc, Kc, or both?
Kc remains unchanged, Qc changes until it equals Kc again.
What happens to Qc relative to Kc when a reactant is added to the system at equilibrium?
Qc < Kc reaction shifts right.
If a gaseous equilibrium mixture is compressed and the number of gas moles is greater on the reactant side, what will the system do?
shift to products, towards the side with fewer gas moles
If Kc decreases after raising the temperature, what can you conclude about the reaction?
reaction is exothermic
Le Chatelier's Principle predicts the direction of a shift, but now how far the reaction goes. What quantity determines the new equilibrium position after the stress?
The reaction quotient.