Chemistry Final Review (Chapter 7&8)

Entropy

(S) Is a measure of the randomness of a chemical system

Calculate the pH of a buffer solution in which Both the acetic acid (acid) and sodium acetate (salt) concentrations are 2.0 × 10−2 M

-The Ka for acetic acid is 1.75 x 10−5 -Solve the Ka expression for [H3O+]:

Nutritional Calorie (large "C" calories)

1 kilocalorie(1kcal)=1,000 calories

Factor that affect reaction rate

1. Structure of the reacting species 2.Molecular shape and orientation 3.Concentration of reactants 4.Temperature of reactants 5. Physical state of reactants 6. Presence of a catalyst

To find concentration of H3O with Molarity give

1.0 x 10^-14 = [H30+][OH-]

Hydronium concentration in pure water @ room temperature

1.0 x 10^-7

Reversible reaction

A process that can occur in both directions •use the double arrow symbol

pH scale

A scale that indicated the acidity and basicity of a solution

0-6 pH

Acidic

Completion

All reactants have been converted to products

Water

Amphiprotic, has both acid and base properties

Activated complex

An extremely unstable, short-lived intermediate complex

Titration

Analytical technique to determine the concentration of an acid or base

Spectator ions

Any ions appearing the same on both sides of equation

Equilibrium reactions

Are incomplete reaction

HA + B -> A- + BH+ •BH+ is the conjugate acid of...

B

8-14 pH

Basic

To predict ΔG

Both ΔH & ΔS needed Ex. H + & S - > G + H- & S+ > G -

Equilibrium reaction

Chemical reaction that do not go to completion

Reduction half reaction

Cl2+ 2e- -> 2Cl-

Exothermic Reactions

Combustion: CH4(g) + 2O2(g)→CO2(g) + 2H2O(g) + 211 kcal

Endothermic Reaction

Decomposition 22 kcal + 2NH3(g) → N2(g) + 3H2(g)

Negative ΔS reaction

Decrease disorder

Acid and base strength

Degree of dissociation

Calorimeter

Device which measures heat changes in calories

Strong acids and bases

Dissociated complete in water

Ionization

Dissociation of acids and bases

ΔH positive

Endothermic

Buffers act to...

Establish an equilibrium between a conjugate acid/base pair

Corrosion

Example of oxidation-reduction reaction

ΔH negative

Exothermic

Bomb calorimeter

Fuel value of food

Reduction

Gain of electrons

Protons

H+ ions

Break apart neutralization reaction into ions

H+(aq) + Cl−(aq) + Na+(aq) + OH−(aq) → Na+(aq) + Cl−(aq) + H2O(l)

Hydronium ion

H3O+

HA + B -> A- + BH+ •A- is the conjugate base of...

HA

Acid base reaction general form

HA+B -> A- + BH+

Neutralization reaction

HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)

Acids

Higher [H3O+] and Lower [OH-]

Base

Higher [OH-] and Lower [H3O+]

High entropy

Highly disordered system Ex: He(g)

Rate..

Increase as concentration increase

Positive ΔS reaction

Increase disorder Ex: phase changes like melting, vaporization and dissolution

Reducing Agent

Is oxidized Loss electrons Causes reduction

Oxidizing agent

Is reduced Gains electrons Cause oxidation

Example: H2(g) + F2(g) --> 2HF(g)

Keq = [HF]^2/ [H^2][F^2]

First Law of Thermodynamics

Law of conservation of energy, energy cannot be created or destroyed

Oxidation

Loss of electrons

Oxidation half reaction

Mg -> Mg^2+ +2e-

7 pH

Neutral

Most endothermic reaction are...

Non spontaneous

Specific heat

Number of calories of heat needed to rise the temperature of 1 f of the substance 1 degree Celsius

Hydroxide ion

OH-

Weak acids and bases

Only small percent dissociates

n

Order of reaction n= 1, first order n=2 , second order

Importance of pH and pH control

Physiology: blood pH shift of 1 pH is fatal

Specific heat equation

Q= m(s) *ΔT*SH(water)

Equilibrium

Rate and reversibility of reaction

The Temperature of Reactants

Rate increases as the temperature increase

The Concentration of Reactants

Rate is related to the concentration of one or more of the reacting substance

For a reaction A > products

Rate= k[A]^n

Exothermic Reactions

Release energy to the surroundings

Enthalpy

Represents heat energy

Endothermic Reactions

Require energy input from surroundings (absorbs)

ΔS reaction =

S(product) - S(reactants)

Net equation

Shows only changed components H+(aq) + OH−(aq) → H2O(l)

Standard solution in titration

Solution of known concentration

Buffer solution

Solution which resists large changes in pH when either acid or bases are added

Free Energy predicts

Spontaneity of chemical reaction - Negative ΔG, always spontaneous -Positive ΔG, never spontaneous

Most exothermic reactions are...

Spontaneous

LeChatelier's Principle

States that if a stress is placed on a system in equilibrium, the system will respond by altering equilibrium

Thermodynamics

Study of energy, work and heat

Indicator

Substance which changes color as pH changes

Bases

Taste bitter, are slippery, are corrosive

Acids

Taste sour, dissolve some metals, cause plant dye to change color

Conjugate Acid-Base Pair

The acid and base on opposite sides of the equation

Calorimetry

The measurement of the heat energy changes in a reaction

Activation energy (Ea)

The minimum amount of energy required to initiate a chemical reaction

Dynamic equilibrium

The rate of the forward process in a reversible reaction is exactly balanced by the rate of the reverse process

Neutralization reaction

The reaction of an acid with base to produce a salt and water

Kinetics

The study of the rate (or speed) of chemical reaction

Second Law of Thermodynamics

The universe spontaneously tends toward increasing disorder or randomness

Low entropy

Well organized system Ex: Na(s)

Conjugate Base

What acid becomes after donating it's protons

Conjugate Acid

What base becomes after accepts a proton

Enthalpy change, ΔH

What is the name of and symbol of the thermodynamic quantity that represents the heat absorbed or liberated in a chemical reaction at constant pressure

Free energy, ΔG

What thermodynamic quantity is the ultimate predictor of reaction spontaneity

Equivalence point

When mole of H3O+ and OH- are equal

Calculate the pH of a buffer solution

[H3O+]= Ka [acid]/[conjugate base]

Ka =

[H3O+][CH3COO−]/ [CH3COOH]

K(w) =

[H3O+][OH-]

Change in Enthalpy

energy difference between the products and reactants of a chemical reaction

pH equation

pH= -log[H3O+]

Example rate equation: A+B --> products

rate= k[A]^n[B]^m

Free Energy

ΔG Represents the combined contribution of enthalpy and entropy values for a chemical reaction

Bronsted-Lowry

•Acid: proton/H+ donor •Base: proton/ H+ accept

Arrhenius theory

•Acids: dissociated to produce hydrogen ions (H+) •Bases: dissociated produced hydroxide ions (OH-)

Common Example of stressed added to a system:

•change in concentration of product or reactant •a change in temperature •change in pressure