Acid-Base Equilibrium
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Concept/Facts / Terminology
Formula Indicators
Formula Indicators
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Base
Opposite of acids
Dissolves in water to generate hydroxide ions (OH-)
Properties are
Is able to be in the form of a liquid and a solid
Generates a bitter taste
Considered to be one of the best conductors for electricity
Able to react with an acid
Tends to generate corrosion (corrosive) and is flammable
Does not use metals to generate hydrogen
Cause Litmus paper to react and become blue
Causes bromthymol blue to react and become blue
Causes phenolphthalein to react and become pink
Considered to be a strong base, due to the fact that it is soluble when present around water molecules
Examples
KOH
NaOH
Considered a weak base when it barely dissolves in water
Examples
Fe(OH)3
Al(OH)3
Common bases are
Sodium hydroxide (NaOH)
Potassium hydroxide (KOH)
Calcium hydroxide (Ca(OH)2)
Sodium carbonate (Na2CO3)
Sodium bicarbonate (NaHCO3)
Ammonium hydroxide (NH4OH)
Acid
Dissolves in water to generate hydrogen ions (H+)
Properties are
Can change from a liquid to a solid
Generates a sour taste
Considered to be one of the best conductors for electricity
Cause Litmus paper to react and become red
Causes bromthymol blue to react and become yellow
When introduced to carbonates, a reaction would occur producing CO2 gas
Tends to generate corrosion (corrosive)
Hydrogen gas is generated when an acid reacts with different metals like Zn, K, Na, Mg, and etc.
Considered a strong acid when the acid ionizes completely
Examples
Fe(OH)3
Al(OH)3
Considered a weak acid when the acid barely ionizes
Examples
Organic acids
CH3COOH
Common acids are
Hydrochloric acid (HCl)
Sulphuric acid (H2SO4)
Nitric acid (HNO3)
Acetic acid (CH3COOH)
Calculating pOH for weak acids/bases
Find the pH value first using the pH formula:
[H+] = 10-pH
Find the concentration of OH- using this formula:
pOH = -log [OH-]
The pOH formula is used and the found pH value is subbed in
pH + pOH = 14
The formula then switched to leave the pOH value alone to become
pOH = 14 - pH
Relationship between Ka, Kb, and Kw
Ka = acidity constant
Kb = basicity constant
Kw = water constant
The relationship between Ka and Kb is that they both depend on pressure and temperature
The sum of Ka and Kb is what results in the formation of constant water which would be Kw
Arrhenius Theory
Swedish scientist
Developed the most common ways to state acids and bases
Calculating pH for strong acids/bases
pH formula is:
pH= -log [H+]
When trying to find the concentration of [H+] and the pH is given. The formula would be:
[H+] = 10-pH
Considered an acid when the pH is below 7
Considered a base when the pH is above 7
Considered a neutral substance when the pH is at 7
Bronsted Lowry Theory
Acids are proton donors
Bases are proton recipients
Water can be considered as acid and base
Every acid-base pairs can react to produce brand new conjugated acid and a brand new conjugated base
A pair with a strong base has a weak acid and a pair with a weak base has a strong acid
Acids and Bases Combined Together
The chemical properties of acids can be neutralized by bases
Water is generated when both are mixed
H+(aq) + OH- (aq) ⇌ H2O (l)
A very low amount of water dissociates into H+ and OH- ions because H2O is considered to be a constant factor
The equilibrium constant for water:
Kw = [H+][OH-] = 1.0 x 10-14 at 25oC
Determining concentrations in titrations
The concentration of titration:
na x Ma x Va = nb x Mb x Vb
stands for
na = amount of hydrogen ions that are given by the acid per molecule
Ma = molarity of the acid
Va = volume of the acid
nb = amount of hydroxide ions that are given by the base per molecule
Mb = molarity of the base
Vb = volume of the base