AP Chemistry Comprehensive Study on Unit 7: Equilibrium Concepts and Reactions

Equilibrium constant expression

k= [products]/[reactants]

K>1

more products than reactants at equilibrium

Forward reaction

Reactants to Products

Reverse reaction

Products to reactants

K<1

more reactants than products at equilibrium

K=1

concentration of products = concentration of reactants

Solids and liquids are...

completely omitted from calculations in equilibrium expressions

How is Q calculated?

Same way as Kc, [products]/[reactants]

What is isolectronic with O2-?

F-

What is the oxidation number of oxygen in H2O?

2-

At equilibrium what is true of K and Q?

K = Q

Removing product according to Le Chatelier causes the reaction to

shift right, towards products

Removing reactant according to Le Chatelier causes the reaction to

Shift left, towards reactants

Increasing volume according to Le Chatelier causes the reaction to

decrease in pressure and shifts toward the side with the more moles of gas

According to Le Chatelier, in an endothermic reaction, increasing temperature means...

adding reactant, shifts right, and the value of K increases because the concentration of the products increase and the concentration of the reactants decrease.

In an endothermic reaction, decreasing temperature means...

removing reactant, shifts left, value of K decreases because the concentration of the products decrease and the concentration of the reactants increase.

In an exothermic reaction, increasing temperature means...

adding product, shifts left, value of K decreases because concentration of the products decrease and the concentration of the reactants increase.

In a exothermic reaction, decreasing temperature means...

Removing product. Reaction shifts right, value of K increases because the concentration of the products increase and the concentration of the reactants decrease.

Adding an inert gas has what effect on equilibrium?

NO effect (no change in concentration)

If the reaction is reversed, the Kc is

inverted

If the reaction is multiplied, the Kc is

raised to that power

If reaction are added together

multiply Kc

Equilibrium

when the forward and backward rates of reaction are equal resulting in a constant concentration of reactants and products

Unit of Concentration

mol/L

Equilibrium Expression (or Law of Mass Action Expression)

concentration of the products raised to the power of their coefficients divided by the concentration of the reactants raised to the power of their coefficients

The more electronegative atom out of O vs. S

Oxygen

Ionization Energy

Energy needed to remove an electron

Reaction Quotient

Q, used when not sure if you are at equilibrium or not

Q = K

system is at equilibrium

K > Q

When reaction quotient has too many reactants. Reaction shifts to right, starts making products

K < Q

When reaction quotient has too many products. Reaction shifts to left, begins making reactants

PV = nRT

Ideal gas law

Oxidation number of nitrogen in a nitrate ion (NO3)-

5+

Why it is easier to remove the first electron of B over Be

B has a p electron that is slightly further from the nucleus than Be thus requiring less energy to remove

Le Chatelier's Principle

If a stress is imposed on a system at equilibrium the position of the equilibrium will shift in a direction that reduces that stress

Number of sig figs in 101,200

4

Le Chatelier effect of adding pressure (decreasing volume)

Shifts in direction of least number of moles

Le Chatelier effect of adding heat to endothermic reactions

Shifts towards products; increases value of K

Catalyst

has no effect on the position of equilibrium but lowers activation energy, increasing the rate of forward and reverse reactions (gets to equilibrium faster)