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