Chem 1007 Test 3

What is Q?

The reaction quotient

Lewis Acid

e- pair acceptor

Lewis Base

e- pair donor

Conjugate Acid-Base Pairs

A pair of substances that differ by H+

Acidic

[H+]>[OH-]

Neutral

[H+]=[OH-]

Basic

[H+]<[OH-]

How to calculate pH

pH=-log[H+]

How to calculate pOH

pOH=-log[OH-]

How to calculate [H+]

[H+]=10^-pH

pH+pOH=

14

Kw=

1.0×10^-14

Weak Acid Formula

HA(aq)+H20(L)<=>A-+H3O+

Weak Base Formula

B(aq)+H2O(L)<=>BH++OH-

Acid Base Properties (3)

Bond Polarity-The stronger the polarity, the stronger the acid.

Bond Strength-Strong bonds are harder to break

Oxyacids

What is a Buffer Solution

A solution that resists a change in pH when H^+ or OH^- are added

A solution that contains a weak acid & its conjugate base (salt of the conj base)

Steps to create a buffer solution

1. But at desired pH

2. Mix HA & A, then adjust using HCl/NaOH

3. Start with HA, use NaOH to neutralize

4. Start with A, use HCl to form HA

Henderson-Hasselbach Equation

pH=pKa+log[A-]/[HA-]

Theoretical Point on a Titration Curve

Equivalence Point

Experimental Point on a Titration Curve

End Point

Solubility Equilibrium Formula

Solid →← The components of it

Ex: CaF2(s) →← Ca²+ + 2F^-

Factors that Affect Solubility

1. Common Ion Effect-Lowers Solubility

2. pH: Increase pH- Less Soluble, Decrease pH-More soluble

3. Formation of Complex Ions-Increase Solubility

Q=Ksp

Highest conc of ions in solution, will NOT form a ppt(precipitate)

Q>Ksp

A ppt forms

Q<Ksp

A ppt will not form (dissolves)

Spontaneity

Whether a reaction can occur with or without external influences

Spontaneous

Process occurs without any external influence

Nonspontaneous

Requires the input of additional energy

1st Law Exothermic

Tends to be spontaneous

1st Law Endothermic

Tends to be nonspontaneous

What happens to matter?

Tends to be dispersed in a spontaneous process

Entropy

The dispersal of matter and energy

Microstate

A single arrangement of particles that a system may adopt with a specific total energy

Boltzman Equation

S=KlnW

ΔSsys=

q(heat)rev/T

Change in Entropy depends on?

T of system

2nd Law of Thermodynamics

ΔSuniverse=ΔSsystem+ΔSsurroundings (For a spontaneous process)

3rd Law of Thermodynamics

For a pure crystal S=0 at 0K

Which has a lower entropy? Cyclic compounds or Linear compounds?

Cyclic Compounds

ΔSrxn=

[Σn•S^•(products)]-[Σm•S^•(reactants)]

ΔSsurr=

-ΔHrxn/T

Gibbs Free Energy Equation

ΔG=ΔH-TΔS

ΔG<0

Spontaneous

ΔG>0

Nonspontaneous

Exothermic, Disorder, Independent Temp

Always Spontaneous

Endo, ordered, Independent T

Always Nonspontaneous

Exo, ordered, low temp

Spontaneous

Exo, ordered, high temp

Nonspontaneous

Endo, disordered, high temp

Spontaneous

Endo, disordered, low temp

Nonspontaneous

Solving for K formula

K=e^-ΔG/RT

R value equal

8.314 J/mol•K

Reduction

Gain of electrons

Oxidation

Loss of electrons

Oxidizing agent

Causes a substance to be oxidized, by being reduced

Reducing agent

Cause a substance to be reduced, by being oxidized

Salt Bridge

Provides Charge balance

Where do cations go?

The cathode

Where do Anions go?

To the anode

Where do electrons move through on a Voltaic cell

Through the wire

Where do the ions move through in a Voltaic cell

Through the solution

Steps to balancing redox reactions

1. Divide reaction by half-reaction

2. Balance all atoms except H&O

3. Balance O by adding H2O to opposite side

4. Balance H by adding H as needed

   IF BASE ADD OH FOR H

5. Balance charge by adding e-

6. e- gained must equal e- lost, multiply half rxn as needed

7. Add & simplify half rxns

8. Check to see if charges balance

9. Check to see if atoms balance