Chem II Midterm 1

“Normal” ___ Point

Means atmospheric pressure is equal to 1 atm

Vapor Pressure Definition (P^o)

The partial pressure of the vapor phase in dynamic equilibrium w/ a condensed phase

Dynamic Equilibrium Definition

The rate or speed of the forward rxn is the same as the rate of the reverse rxn

• aka for every water that evaporates, another condenses so they cancel out

Relationship Between Vapor Pressure and Temperature

Direct relationship

Relative Humidity Formula

PH2O = partial pressure of water

P^oH2O = vapor pressure of water

RH is 100% when…

… when partial pressure = vapor pressure

Boiling Point Definition

The temperature at which the vapor pressure is equal to the atmospheric pressure

Relationship Between Boiling Point and Vapor Pressure

Inverse Relationship

Clausius-Clapeyron Equation

Always make P2^o the unknown of solving for it

Temperature = Kelvin

R = 8.314 × 10^-3 kJ/mol*K

At 25 C, ΔHvap = 44 kJ/mol

At 100 C, ΔHvap = 40.65 kJ/mol

At 25 C, ΔHvap is …

44 kJ/mol

At 100 C, ΔHvap is …

40.65 kJ/mol

Phase Diagram

Normal Melting/Freezing Point on Phase Diagram

Normal Boiling Point on Phase Diagram

Low pressure + high temp is what phase?

Gas phase

Colligative Properties Definition

Physical properties that depend on the number of solute particles in solution

• interested in concentration of solute

Molarity (M) Formula

Osmotic Pressure (π) Formula

π has to be in atm

T has to be in Kelvin

What R do you use to find osmotic pressure?

0.08206 L*atm/mol*K

Mass Percent

Molality

Temp dependent concentration

Mole Fraction

Relationship Between Two Mole Fractions

Can be used if there’s two unknowns

The Four Colligative Properties

• Vapor Pressure Lowering

• Boiling Point Elevation

• Freezing Point Depression

• Osmosis

Vapor Pressure Lowering Definition

Adding a nonvolatile solute lowers vapor pressure of solvent

Raoult’s Law:

a) Equation for Reduced Vapor Pressure of Solvent in Solution

Raoult’s Law:

a) Equation for Reduced Vapor Pressure of Solute in Solution

Formula for Total Vapor Pressure in Solution

Relating Mole Fraction of Solvent and Solute

Ideal Solutions Definition

Solutions where solute-solvent intermolecular forces are the same strength as solvent-solvent intermolecular forces

If solute-solvent intramolecular forces are STRONGER than solvent-solvent …

• You get negative deviation

• Boiling Point is higher than ideal solution’s to reach 1 atm

• Raoult’s Law = overestimation

If solute-solvent intramolecular forces are WEAKER than solvent-solvent …

• You get positive deviation

• Boiling Point is lower than ideal solution’s to reach 1 atm

• Raoult’s Law = underestimation

Boiling Point Elevation Definition

Adding a solute raises the boiling point of the solvent b/c it lowers vapor pressure

Equation for Change in Boiling Point

Kb is specific to the solvent

For nonelectrolytes, i = 1

Freezing Point Depression Definition

Adding a solute lowers the freezing point of the solvent

Equation for Freezing Point of Solution

Equation for Change in Freezing Point

Kf is dependent on solvent

Equation for Boiling Point of Solution

Osmosis Definition

The flow of solvent through a semi-permeable membrane from a region of low solute concentration to one of high solute concentration

Osmotic Pressure Definition

The pressure to reverse osmosis

Kinetics Definition

The study of the rate (speed) of reactions and why

Equation Relating Average Rate of a Reaction, Reactant, & Product

Instantaneous Rate Definition

How fast a reaction goes

Relation Between Concentration and Speed of Reaction

They are directly related

• high concentration = faster rxn

Rate Law: Relates Rate of Reaction to Concentration

x and y = individual rxn orders

• if = 1, don’t write out 1

Formula for Units of k

Formula for Overall Rxn Order

Elementary Rxn Definition

1 step/collision rxn

Composite Rxn Definition

Rxn with multiple elementary steps

• opposite of elementary rxn

Method of Initial Rates Definition

Using different trials to determine individual rxn orders

Steps to Determine Individual Rxn Order

1. Determine what trials to use to determine order for [A]

• use trials where the non-finding concentration’s values are the same

2. Identify if [A] exactly doubled between both trials

• Yes: Compare value of rates of both trials

  • Rate doesn’t change → 0 order

  • Rate 2X → 1st order

  • Rate 4X → 2nd order

• No: Use eqn and solve for order

3. Do same process to find order for [B]

Integrated Rate Laws Definition

Laws that relate concentration to time

Zero Order Integrated Rate Law Formula

Zero Order Integrated Rate Law Graph

Slope = -k

First Order Integrated Rate Law Formula

First Order Integrated Rate Law Graph

Slope = -k

Second Order Integrated Rate Law Formula

Second Order Integrated Rate Law Graph

Slope = k

High mi means …

Larger boiling point elevation

• higher boiling point

Larger freezing point depression

• lower freezing point

Low mi means …

Lower boiling point elevation

Lower freezing point elevation

When Calculating Molality, If Mass of Solvent Isn’t Given …

You can assume the denominator (kg solvent) is just 1 kg

• if you’re given a mass, just convert it to kg

For Carbohydrate Compounds, i is usually

1

Equation for Average Rate of Formation

Product Specific

Equation for Average Rate of Consumption / Disappearance

Reactant specific

If Solute-Solvent Interactions are Weaker than Solvent-Solvent, Then Actual Vapor Pressure …

Will be higher than that predicted by Raoult’s law

If Solute-Solvent Interactions are Stronger than Solvent-Solvent, Then Actual Vapor Pressure …

Will be lower than that predicted by Raoult’s law

In Integrated Rate Laws, Time is In Units of …

Seconds

• may have to convert to minutes if needed

Rate Law If x = 0

Rate Law If x = 1

Rate Law If x = 2

In Clausius-Clapeyron Eqn, ∆Hvap must be in …

J/mol

• so multiply kJ by 1000 to get J

i (Van’t Hoff factor) depends on …

Solute

Density Formula

A liquid-liquid solution is ideal if …

1. It obeys Raoult’s Law

2. Solute-solute, solvent-solvent, and solute-solvent interactions are very similar

Graph for r = k

Graph for r = k[A]

Graph for r = k[A]²