MCAT General Chemistry Review 6

Arrhenius Acid

 

Arrhenius Base

Anything that produces hydrogen ions in an aqueous solution.

 

Anything that produces hydroxide ions in an aqueous solution.

Bronsted and Lowry Acid

 

Bronsted and Lowry Base

Anything that donates a proton

 

Anything that accepts a proton

Lewis Acid

 

Lewis Base

Anything that accepts a pair of electrons.

 

Anything that donates a pair of electrons.

pH Measurement
pH = -log[H+]
Conjugate Acid

The resultant product of a base in a reaction.

Conjugate Base
The resultant product of a acid in a reaction.
Amphoteric
Substance that act as an acid or base dependent on the environment.
Strong Acids

Hydroidic acid,     HI

Hydrobromic acid,  HBr

Hydrochloric acid,  HCl

Nitric acid,               HNO3

Perchloric acid,         HClO4

Chloric acid,             HClO3

Sulfuric acid,             H2SO4

Strong Base

Sodium Hydroxide,      NaOH

Potassium Hydroxide, KOH

Amide Ion,               NH2

Hydride Ion,          H

Calcium Hydroxide,         Ca(OH)2

Sodium Oxide,           Na2O

Calcum Oxide,          CaO

Polyprotic
Can donate more than one proton
How Molecular Structure Affects Acid Strength

1. Strength of the bond holding the hydrogen to the molecule

2. the polarity of the bond

3. the stability of the conjugate base

Hydrides
Binary compounds that contain hydrogen
Autoionization of Water

Pure water reacting with itself to form hydronium and hydroxide ions.

 

H20 + H20 –> H- + H30+

Kw Equilibrium Constant

Kw = [H+][OH-]

 

Kw =10-14

 

KaKb=Kw

pKw of Water

pKw=pH + pOH

pKa + pKb = pKw

Acid Dissociation Constant, Ka
Ka = [H+][A-]/[HA]
Base Dissociation Constant, Kb

Kb = [OH-][HA]/[A-]

Ka = ?

Ka = [H+][A-]/[HA]

 

If we know Ka and molar concentration of the acid, and need to find the pH, we can solve for

x*x/.01-x = Ka which reduces to

x2/.01=Ka

Salt

Ionic compounds that dissociate in water.

When salts dissociate they often create acidic and basic conditions.

Titration

Drop by drop mixing of an acid and a base.

 

Performed to find the concentration of some unknown by comparing it with the concentration of the titrant.

Equivalence Point (Stoichiometric point)
Point for a monoprotic acid in titration when there are equal equivalents of acid and base in a solution.
Titration with a base stronger than the acid:
Equivalence point is above 7
Titration with the acid stronger than the base.
Equivalence point below 7
Half equivalence point

Point where one half of the acid has been neutralized by the base.

 

Concentrations of the acid equal to the concentration of the conjugate base.

 

This shows the point where the solution is the most well buffered.

 

pH of the solution = pKa of the acid.

Buffered Solution
We can add the largest amount of base or acid with the least amount of change in pH.
Henderson-Hasselbalch Equation

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

 

When [A-]=[HA], pH=pKa because log(1) = 0 

Indicator
A weak acid whose conjugate base is a different color.
Range
The pH values of the two points of color change. Can be predicted by the HH Equation
Endpoint
The point where an indicator changes color.
x

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