Chemical Equilibrium and Analysis: Final Exam Review

London/Dispersion Forces

Random interactions between molecules with no permanent dipoles (weakest force)

Dipole-Dipole Forces

Between molecules with permanent dipoles (between polar molecules)

Ion-Dipole Forces

Found in solvation of ions (would exist between Cl- and H2O-)

Hydrogen Bonding Forces

Between the hydrogen atom of one molecule and electronegative atom like N, O, or F of another molecule (between oxygen and hydrogens in different molecules)

Which intermolecular force is the strongest? Which is the weakest?

Strongest: Ion-Dipole Forces

Weakest: London/Dispersion Forces

Enthalpy (ΔH)

Total energy (heat) content of a system

Exothermic Processes

Definition: ?

Change in Enthalpy: Positive or Negative?

Heat Energy: Absorbed or Released?

Example: ?

Definition: A transformation in which a closed system releases energy (heat) to the surroundings

Change in Enthalpy: Negative

Heat Energy: Released

Example: Hot Pack

Endothermic Processes

Definition: ?

Change in Enthalpy: Positive or Negative?

Heat Energy: Absorbed or Released?

Example: ?

Definition: A transformation in which a closed system absorbs energy (heat) from the surroundings

Change in Enthalpy: Positive

Heat Energy: Absorbed

Example: Cold Pack

Entropy (ΔS)

Measure of disorder in a system (entropy is positive for formations of solutions, which means a positive value corresponds to an increase in disorder)

- Solutions can be formed in solid, liquid, and gas phases (entropy increases upon formation of solutions in gas and liquid phases)

Unsaturated Solution

Solution contains less solute than limit of solubility

Saturated Solution

Solution is at its limit of solubility

Supersaturated Solution

Solution contains more solute than limit of solubility through slow cooling

Henry's Law

The solubility of a gas in a liquid decreases as temperature increases. Also, the partial pressure of the gas above the solution is proportional to the gas solubility in water

Solid Solute in Aqueous Solutions:

Temperature will increase the solubility of a solid solute in water.

Mass Percent (Weight Percent: wt. %)

Mass (Solute)/ Total Mass (100)

Parts Per Million (ppm)

Equivalent Units: mg/kg = ug/g = mg/L

Parts Per Billion (ppb)

Equivalent Units: ug/kg = ng/g = ug/L

Mole Fraction

Moles (A)/ Total Moles

- Value is always between 0 and 1

- No units

Molarity

Moles (Solute)/ Liters (Solution)= M

Molality

Moles (Solute)/ Kg (Solvent)= m

Colligative Properties

Properties that depend on the concentration of solute particles

Vapor Pressure Lowering

Boiling Point Elevation

Boiling point increases as solute particles increase

Boiling Point Elevation Equation

ΔTb = imKb

- Van't Hoff factor, i, relies on solute particles

- Molality of solute, m

- Boiling point elevation constant Kb relies on solvent

A large Kc value will...

favor the products.

A small Kc value will...

favor the reactants.

What happens to Kc if the coefficients in the reaction are halved? (dividing coefficients)

Kc becomes the square root of what it was before

What happens to Kc if the coefficients in the reaction are doubled? (multiplying coefficients)

Kc gets raised to the 2nd power

What happens to Kc if the coefficients in the reaction are tripled? (multiplying coefficients)

Kc gets raised to the 3rd power

What happens to Kc if the reaction is reversed? (reversing reaction)

-Exchange the products and reactants so K(prime) is the reciprocal of the original K expression

- Calculate 1/K

- K(reversed)= 1/K(original)

What happens to Kc when reactions are added together?

Heterogenous Equilibrium

Species exist in more than one state (gas, liquid, or solid)

Homogeneous Equilibrium

All species in the same state (gas, liquid, or solid)

If the reaction quotient, Q, is equal to K the reaction...

is at equilibrium.

If the reaction quotient, Q, is greater than K the reaction...

will proceed toward reactants to reach equilibrium.

If the reaction quotient, Q, is less than K the reaction...

will proceed toward the products to reach equilibrium.

Adding to reactants causes the equilibrium to...

shift to the right.

Removing reactants causes the equilibrium to...

shift to the left.

Adding to products causes the equilibrium to...

shift to the left.

Removing products causes the equilibrium to...

shift to the right.

An increase in volume shifts the equilibrium towards the side of the reaction with...

more moles of gas.

A decrease in volume shifts the equilibrium to...

reduce the moles of gas.

Endothermic Reactions

Equation: ?

ΔH : > 0, or < 0

Addition of Heat (Temp. Increase): ?

Removal of Heat (Temp. Decrease): ?

Equation:

Reactants + Heat <=> Products

ΔH: > 0

Addition of Heat: Shifts equilibrium to the products

Removal of Heat: Shifts equilibrium to the reactants

Exothermic Reactions

Equation: ?

ΔH: > 0, or < 0

Addition of Heat (Temp. Increase): ?

Removal of Heat (Temp. Decrease): ?

Equation:

Reactants <=> Products + Heat

ΔH < 0

Addition of Heat: Shifts equilibrium to the reactants

Removal of Heat: Shifts equilibrium to the products

Adding a catalyst to a reaction...

increases the rate of the reaction, so equilibrium is reached more quickly.

Arrhenius Concept

ACID= If an acid is dissolved in water, it increases [H+]

BASE= If a base is dissolved in water, it increases [OH-]

*Only applies to aqueous solutions

Bronsted-Lowry Concept

ACID= Proton donor

BASE= Proton acceptor

Conjugate ACID= Base + proton

Conjugate BASE= Acid - proton

Lewis Concept

ACID= Electron pair acceptor

BASE= Electron pair donor

Amphoteric

Substance can act as an acid or as a base

Amphiprotic

Substance can accept or donate a proton

Monoprotic Acid

Has one acidic hydrogen

Ex(s): HCl, CH3COOH

Diprotic Acid

Has two acidic hydrogens

Ex(s): H2SO4, H2CO3

Polyprotic Acid

Has more than two acidic hydrogens

Ex: H2PO4

Seven Strong Acids:

HCl (Hydrochloric Acid), HBr (Hydrobromic Acid), HI (Hydroiodic Acid), HNO3 (Nitric Acid), HClO3 (Chloric Acid), HClO4(Perchloric Acid), H2SO4 (Sulfuric Acid)

Eight Strong Bases:

LiOH (Lithium Hydroxide), NaOH (sodium Hydroxide), KOH (Potassium Hydroxide), RbOH (Rubidium Hydroxide) , CsOH (Cesium Hydroxide) , Ca(OH)2 (Calcium Hydroxide), Sr(OH)2 (Strontium Hydroxide), Ba(OH)2 (Barium Hydroxide)

The solubility of gas will decrease with an ____ in temperature.

increase

For a gas phase solute, what would an increase in temperature do to the solubility?

Decrease

For the formation of solution, would there be a positive or negative change in entropy?

Positive

Which Kc value would indicate that equilibrium favors the reactants?

If Kc is < 1 (negative)

As the pKa of an acid decreases...

the acid becomes stronger.

Amines

Identify how many "R" groups are present

Ex: Ammonia- NH3

Primary Amine: RNH2

Secondary Amine: R2NH

Tertiary Amine: R3N

if the Ka value is less than the Kb value...

the salt is going to partially dissolve.