Acid-Base Equilibrium

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Acid-Base Equilibrium

Determining concentrations in titrations

stands for

Vb = volume of the base

Mb = molarity of the base

nb = amount of hydroxide ions that are given by the base per molecule

Va = volume of the acid

Ma = molarity of the acid

na = amount of hydrogen ions that are given by the acid per molecule

The concentration of titration:

na x Ma x Va = nb x Mb x Vb

Acids and Bases Combined Together

Water is generated when both are mixed

The equilibrium constant for water:

Kw = [H+][OH-] = 1.0 x 10-14 at 25oC

A very low amount of water dissociates into H+ and OH- ions because H2O is considered to be a constant factor

H+(aq) + OH- (aq) ⇌ H2O (l)

The chemical properties of acids can be neutralized by bases

Bronsted Lowry Theory

A pair with a strong base has a weak acid and a pair with a weak base has a strong acid

Every acid-base pairs can react to produce brand new conjugated acid and a brand new conjugated base

Water can be considered as acid and base

Bases are proton recipients

Acids are proton donors

Calculating pH for strong acids/bases

Considered a neutral substance when the pH is at 7

Considered a base when the pH is above 7

Considered an acid when the pH is below 7

When trying to find the concentration of [H+] and the pH is given. The formula would be:

pH formula is:

pH= -log [H+]

Arrhenius Theory

Developed the most common ways to state acids and bases

Swedish scientist

Relationship between Ka, Kb, and Kw

The sum of Ka and Kb is what results in the formation of constant water which would be Kw

The relationship between Ka and Kb is that they both depend on pressure and temperature

Kw = water constant

Kb = basicity constant

Ka = acidity constant

Calculating pOH for weak acids/bases

The formula then switched to leave the pOH value alone to become

pOH = 14 - pH

The pOH formula is used and the found pH value is subbed in

pH + pOH = 14

Find the concentration of OH- using this formula:

pOH = -log [OH-]

Find the pH value first using the pH formula:

[H+] = 10-pH

Acid

Common acids are

Acetic acid (CH3COOH)

Nitric acid (HNO3)

Sulphuric acid (H2SO4)

Hydrochloric acid (HCl)

Considered a weak acid when the acid barely ionizes

CH3COOH

Organic acids

Considered a strong acid when the acid ionizes completely

Al(OH)3

Fe(OH)3

Hydrogen gas is generated when an acid reacts with different metals like Zn, K, Na, Mg, and etc.

Tends to generate corrosion (corrosive)

When introduced to carbonates, a reaction would occur producing CO2 gas

Causes bromthymol blue to react and become yellow

Cause Litmus paper to react and become red

Generates a sour taste

Can change from a liquid to a solid

Dissolves in water to generate hydrogen ions (H+)

Base

Common bases are

Ammonium hydroxide (NH4OH)

Sodium bicarbonate (NaHCO3)

Sodium carbonate (Na2CO3)

Calcium hydroxide (Ca(OH)2)

Potassium hydroxide (KOH)

Sodium hydroxide (NaOH)

Considered to be a strong base, due to the fact that it is soluble when present around water molecules

Examples

NaOH

KOH

Properties are

Causes phenolphthalein to react and become pink

Causes bromthymol blue to react and become blue

Cause Litmus paper to react and become blue

Does not use metals to generate hydrogen

Tends to generate corrosion (corrosive) and is flammable

Able to react with an acid

Considered to be one of the best conductors for electricity

Generates a bitter taste

Is able to be in the form of a liquid and a solid

Dissolves in water to generate hydroxide ions (OH-)

Opposite of acids

Ledgend

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Formulas

Formula Indicators

Concept/Facts / Terminology

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