Chemistry II = Exam 2

What is the second law of thermodynamics?

Any spontaneous process will result in an increase in the total entropy of the universe.

If the change in entropy of the universe is POSITIVE, the reaction is

spontaneous

If the change in entropy of the universe is NEGATIVE, the reaction is

non spontaneous

If the Gibbs free energy of the system is NEGATIVE, the reaction is

Exergonic and Spontaneous

If the Gibbs free energy of the system is POSITIVE, the reaction is

Endergonic and Non spontaneous

Under what conditions will the spontaneity of a reaction just depends?

When change in H and -T(change in S) have opposite signs.

If H is negative and S is positive, then

The reaction is spontaneous at ALL temperatures.

If H is positive and S is negative, then

The reaction is non spontaneous at ALL temperatures

If H and S are both negative, then

The reaction is spontaneous at only low temperatures

If H and S are both positive, then

The reaction is spontaneous at only high temperatures

What is the Gibbs Free Energy of Formation (G_f)?

The change in Gibbs free energy of reaction needed to make 1 mol of a compound from it’s elements.

What is a solute?

What is being dissolved in a solution

What is a solvent?

What the solute is being dissolved IN.

What are the IMF’s from strongest to weakest?

Ion-Dipole, Hydrogen Bonding, Dipole-Dipole, Ion-induced Dipole, Dipole-Induced Dipole, and Dispersion.

Define ion-dipole interactions.

Bonds between ionic and polar molecules.

Define Hydrogen Bonding

Bonds between a hydrogen and elements F, O, or N

Define Dipole Dipole Interactions

Bonds between two polar molecules (excluding H bonds)

Define ion-induced dipole interactions

A charged ion approaches a nonpolar molecule

Define dipole induced dipole interactions

Polar bonded to nonpolar molecules

Define Dispersion Forces

Nonpolar bonded to nonpolar, every molecule has this.

What three factors affect solubility?

Temperature, Colligative Properties, and Pressure.

What is Henry’s Law?

At constant temperature, the amount of a given gas dissolved in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.

Define Vapor Pressure Depression

A colligative property which is the pressure of the gas above the liquid when both are in dynamic equilibrium.

Define dynamic equilbrium

Rate of condensation = rate of evaporation

Define Boiling Point Elevation

A colligative property where adding an non volatile solute to a solvent increases the boiling point of the solvent.

Define Freezing Point Depression

A colligative property where adding a non volatile solute to a solvent decreases the freezoing point of a solvent.

Define Osmotic Pressure

A colligative property where the pressure required to stop the movement of solvent through a semipermeable membrane from a solution with lower solute concentration to one with higher solute concentration.

What are the 4 colligative properties?

Vapor Pressure Depression, Boiling Point Elevation, Freezing Point Depression, and Osmotic Pressure.

What determines the vapor pressure of a molecule?

Molecules with weaker IMF’s have a larger vapor pressure and molecules with stronger IMF’s have a lower vapor pressure.

When does the boiling point increase?

When the number of solute particles increase

Why is salt added to ice?

The process lowers the freezing point of the ice, allowing for the ice to melt quicker.

What is true about a reaction at equilbrium?

The rates of the forward and reverse reaction is equal.

If K is less than 1:

The reverse reaction is favored, creating more reactants

If K is greater than 1:

The forward reaction is favored, creating more products

If k is = 1

Neither reaction is favored.

What does a catalyst do to a reaction that hasn’t reached equlibrium?

It shortens the time it takes to reach equilibrium but DOES NOT change the equilibrium concentrations

If Q is LESS THAN K,

The reaction will go towards the products

If Q is GREATER than K

The reaction will go towards the reactants.

If Q = K

The reaction is at equilibrium

In an equilbirum expression: the concentration of a pure liquid or solid is denoted as

1

What are the strong acids?

HCl, HBr, HI, H2SO4, HNO3, HClO4, HClO3

What is the ONLY thing that changes Kc for Le Chatelier’s Principle?

Temperature is the only thing that can change Kc.

What is the Arrhenius Definition of an Acid?

A substance that increases the amount of H+ ions in an aqueous solution

What is the Arrhenius Definition of an Base?

A substance that increases the amount of OH- ions in an aqueous solution

Weak acids only:

Partially dissociate in aqueous solutions

A small Ka value means that

Equilibrium favors the reactants, which meanas that the acid partially disassociates.

The Bronstead Lowry definition for an ACID is:

Whatever is a proton/ H+ donor

The Bronstead-Lowry defintion for a BASE is:

Whatever is a proton/H+ acceptor

What does the value of Ka tell you about the acid?

If the Ka is lower, it means that the pH is higher, making it a weak acid.

What is a conjugate acid?

It is the base that gains a proton

What is a conjugate base?

It is the acid that loses a proton.

What is pKa?

It is a measure of acidity that uses the Acid Dissociation Constant.

What exactly is Q?

The relative amount of reactants and products in a mixture at any given moment.

How does temperature affect Kw?

As temperature increases, the value of Kw increases

When can you use the equation pH = 14 - pOH

When the temperature is 25 C.

As Kb gets lower,

it becomes less basic

The conjugate base of a strong acid is

Neutral

The conjugate acid of a weak base is

Acidic