SCH4U - Unit 4 Equlibriums (? wtf is this unit called)

Dynamic Equilibrium

A balance between forward and reverse processes occurring at the same rate

Forward Reaction

The reaction that forms products from reactants.

Reverse Reaction

The reaction that forms reactants from products.

Phase Equilibrium

A dynamic equilibrium between different physical states of a pure substance in a closed system

Chemical Reaction Equilibrium

A dynamic equilibrium between reactants and products of a chemical reaction in a closed system

Reversible Reaction

A chemical reaction in which the products re-form the original reactants

What is 'Equilibrium'?

Equilibrium is reached when the rate of the forward reaction is equal to the rate of the backward reaction

Equilibrium Constant

the ratio of product concentrations to reactant concentrations at equilibrium, with each concentration raised to a power equal to the number of moles of that substance in the balanced chemical equation

Homogenous Equilibria

All reactants and products are in the same phase

Heterogenous Equilibria

Equilibria in which reactants and products are in more than one phase

Le Chatelier's Principle

If changes are made to a system in equilibrium, the reaction will shift in the direction that will reduce or minimize the change
Essentially, when you remove something from a system at equilibrium, the system shifts in a way that will replace what you've taken away

What factors can cause a shift in equilibrium?

- Concentration (substance added, rxn shifts away from that side)
- Pressure (pressure increased, rxn shifts to side that produces fewer moles)
- Temperature (Increased temp, rxn will shift to side that absorbs heat)

Reaction Quotient (Q)

Similar to the equilibrium constant, but we look at the initial concentrations
It measures the relative amounts of products and reactants present during a reaction at a particular point in time

Predicitons on equilibrium shifts based off Q and K(sub c)

1. Q = K(sub c) - nothing will change
2. Q > K(sub c) - initial concentration of of products is larger than the initial of the reactamts, eqm will shift towards reactants (left)
3. Q < K(sub c) - Initial concentration of reactants is greater than initial of products, eqm will shift towards products (right)

Solubility

The ability of a solid, liquid, or gaseous chemical substance (referred to as the solute) to dissolve in solvent (usually a liquid) and form a solution

Solubility Product

The product of the concentration of the ions that exist in equilibrium with the solid compound in a saturated solution.

Difference betweem Solubility and Solubility Product Constant

solubility refers to the extent to which a substance can dissolve in a solvent, while the solubility product constant (Ksp) is The percentage of how much will and won't dissolve (will it favour the products or reactants?)

Trial Ion Product

the reaction quotient applied to the ion concentrations of a slightly soluble salt

The Common Ion Effect

A decrease in the solubility of an ionic compound caused by the addition of a common ion

In other words: If you add something that already has one of the ions present, It wouldn't be as soluble as it would be because it would shift the le chatelier's to the other side since it acts as a product

How does Le Chatelier's principle explain the common ion effect?

If you're adding product, you're shifting to the reactants side

Separation by Precipitation

Uses the common ion effect and K(sub sp) values for the solids to determine wehter complete separation of two ions can be accomplished

Enthalpy (∆H)

Describes heat given off or absorbed during a reaction

Entropy (∆S)

Descrives the disorder associated with the reaction

Enthalpy vs. Entropy changes

Enthalpy changes measure the heat/energy while entropy changes measure the disorder/randomness (spontaneity)

What do we use Enthalpy and Entropy for?

We can predict whether or not a reaction will proceed spontaneously

-∆H and +∆S reactions are favoured
+∆H and -∆S reactions are unfavoured

+∆H and +∆S, Gibbs Free Energy - must be calculated to determine favourability
-∆H and -∆S, Gibbs Free Energy - must be calculated to determine favourability

How does the second law of thermodynamics affect the operation of an automobile?

Increases entropy as it turns the liquid gas into gas
Produces heat
Loses rubber because of friction on the road
Oxidation - it's wearing down the metals and rusting lols

Gibbs Free Energy

∆G = ∆H - T∆S

- Units are kJ/mol
- Reaction is favoured if negative
- Related to the Equilibrium Constant

Free Energy

The energy available to do useful work.

Spontaneous Reaction

Once you give it the activation energy, it'll continue on spontaneously

Bond Energy

the energy required to break a chemical bond and form neutral isolated atoms

Second Law of Thermodynamics

All changes either directly or indirectly increase the entropy of the universe. Mathematically ΔS universe > 0

Third Law of Thermodynamics

as the temperature of a system approaches absolute zero (0 Kelvin or -273.15°C), the entropy (disorder) of a perfect crystal approaches zero.

Amphoteric

In the Brønsted-Lowry model, a substance capable of acting as an acid or a base in different chemical reactions; a substance that may donate or accept a proton.

Ion Product Constant for Water

Kw equilibrium constant for the ionization of water; 1.0 1014

Autoionization of Water

The reaction between two water molecules producing a hydronium ion and a hydroxide ion

Monoprotic

An acid that possesses only one ionizable (acidic) proton

Polyprotic

The ability to accept or donate more than one proton

Bronsted-Lowry Acids and Bases

Acids are proton donors and bases are proton acceptors

Neutralization

The process in which a stoichiometric equivalent of acid is added to a base

Salt

The formataion of an ionic solid as a product of an acid-base reaction. Salts are composed of anions and cations that when dissolved become strong electrolytes

Conjugate Acid and Base Pairs

An acid and a base that differ only through the gain or loss of a single proton
- Acid reactant loses a proton and becomes the conjugate base product
- Base reactant gains a proton and becomes the conjugate acid product

Protic Solvents

Contain an acidic proton and underog autoprotolysis

Aprotic Solvents

No acidic protons

Calculating pH

pH = -log(H+)
The [H+] concentration is the same as the [H+] concentration indicated in an equilibrium constant

Strength of Acids and Bases

Strong acids dissociate entirely in water to give H+ and anion
- The H+ concentration is equal to the strength of the acid
Strong bases dissociate entirely in water to give OH- and cation
- The OH- concentration is equal to the strength of the base

Weak Acids

- Partially dissociate to give H+ in H2O
- Equilibrium constant: HA + H2O ↔ H3O+ A-
- The smaller the K (sub a) value, the weaker the acid
- Ex: Carboxylic and Ammonium acids

Weak Bases

- React with water by abstracting a proton
- Equilibrium constant: B + H2O ↔ BH+ + OH-
- The smaller the K (sub b) value, the weaker the base
- Ex: Amines and Carboxylate Anions

Equilibrium Notation for Polyprotic Acids and Bases

- Acids - K (sub 1), K (sub 2), K (sub 3) [commonly used instead of K (sub a1) unless necessary for clarity
- Bases - K ( sub b1), K (sub b2), K (sub b3)
- K (sub 1) and K (sub b1) - indicating acidic or basic species with the most protons

Relationship between acid and conjugate base

- (K (sub a))(K (sub b)) = K (sub w)
- Same for polyprotic, except you must be aware of which acid/base pair is discussed

The Meaning of 'K' (The Equilibrium Constant)

Can tell if a reaction is product or reactant favoured - Conc of products is much greater than reactants at equilibrium = the reaction is strongly product-favoured - vice versa
- Product favoured - K > 1
- Reactant favoured - K < 1

The '100' Rule

If Keq is really small the reaction will not proceed to the right very far, meaning the equilibrium concentrations will be nearly the same as the initial concentrations of your reactants

Ex: 0.20 - x is about 0.20 if x is really tiny (like 1.2x10^-11)

What is Titration

Technique used to determine the concentration of a solution by reacting it with a solution of known concentration.

What is a Titration Curve?

A plot of pH vs the amount of titrant added. Typically the titrant added.

What is a Buffer?

- A mixture of a conjugate acid-base pair that can maintain a nearly constant pH even when diluted or when small amounts of strong acids or bases are added.
- Consists of a weak acid (proton donor) and its conjugate base (proton acceptor)

Titrant

the solution of known concentration that is added to the analyte during a titration.

What is an Endpoint?

Endpoint of a titration is the point at which the titration is complete, usually indicated by a color change in the indicator added to the analyte solution.

In a closed system, how would a catalyst affect the establishment of equilibrium in the system?

It would speed up the forward and reverse rates of reaction without altering the final equilibrium position

Why is the pH of pure water at SATP equal to 7?

Because it's neutral
because it is neutral due to the balance between hydronium and hydroxide ions resulting from autoionization.

Most soft drinks are acidic solutions. When you consume a soft drink, acids are absorbed into the bloodstream. However, the pH of blood remains virtually unchanged. Why?

The pH of blood remains virtually unchanged despite the consumption of acidic soft drinks due to the body's effective buffering systems