10. Proton transfer reactions: acid-base behaviour

The ionic theory

Electrolytes dissociate into freely moving charged particles called ions when dissolved in water or melted

How to calculate the pH of a strong base

First find hydroxide ion (OH^-) concentration, then H⁺ concentration

Experiments to distinguish between strong and weak acids and bases

1. pH measurement

2. Conductivity measurement (strong A&B solutions contain more ions, so are more conductive than weak A&B solutions)

3. Concentration measurement (RoR of strong acids with metals, metal oxides, metal hydroxides, metal hydrogencarbonates, and metal carbonates is greater than that of weak acids)

Alkali

A base that is soluble in water.

rain water pH

5.65

Acid rain

pH<5.6

Wet deposition, due to the acidic oxides dissolving and reacting with water in the air

Acid deposition

Process in which acidic particles, gases, and precipitation leave the atmosphere

Sulfur trioxide

Sulfur dioxide is oxidized by sunlight

Sulfurous acid and sulfuric acid

Sulfur trioxide + water in the air

Nitrogen monoxide, NO

Produced in the internal combustion engine and in jet engines.

Acid rain environmental impact

1. Increased acidity in the soil leaches important nutrients, such as Ca²⁺, Mg²⁺, and K⁺

2. Causes leaching of Al³⁺ ions from rocks → harmful to tress and aquatic life

3. Animals can’t survive lower pH rates

Acid rain impact people

1. Stone containing calcium carbonate, e.g. marble, is eroded by acid rain.

2. Salts can also form within the stone, causing the stone to crack and disintegrate.

3. Acids formed when NOx and SOx dissolve in water irritate the mucous membranes and increase the risk of respiratory illnesses, such as asthma, bronchitis, and emphysema.

4. In acidic water, there is more probability of poisonous ions, such as Cu2+ and Pb2+, leaching from pipes.

Methods to lower or counteract the effects of acid rain

1. Reduce amounts of NOx and SOx formed

   1. Improved engine design

   2. Using catalytic converters

   3. Removing sulfur before, during, and after combustion of sulfur-containing fuels.

2. Switch to alternative methods of energy production

3. Reduce the amount of fuel burned, e.g. by reducing private transport,

4. Liming of lakes (Adding calcium oxide or calcium hydroxide (lime) neutralizes the acidity)

Inflexion point or equivalence point

Area on the graph where the pH changes most rapidly and the line is almost vertical

Concentration of the hydrogen ions

1 x 10^-7 mol dm^-3

pH

power of Hydrogen

K_w

Ionic product constant of water

Monoprotic

Acid/Base can donate/accept 1 proton

Diprotic

Acid/Base can donate/accept 2 protons

Triprotic

Acid/Base can donate/accept 3 protons

Oxidation

Loss of electrons

Reduction

Gain of electrons

Strong Acid and Base Properties

Acid completely dissociates

Irriversible (→)

Have weak conjugates

Weak Acid and Base Properties

Partially dissociates in water

Reversible (are at equilibrium, ←→)

Have Strong conjugates

Strong bases

Ba(OH)₂

NaOH

KOH

LiOH

Metal hydroxides (M-OH)

Strong acids

HCl

HBr

HI

HNO₃

H₂SO₄

Weak bases

Amines (NH(2)-R)

Ammonia (NH₃)

Aminoethane (C₂H₅NH₂)

Carbonates (contain CO₃^2-)

weak acids

organic acids (-COOH)

CH₃COOH

HCOOH

HF

H₃PO₄

HNO₂

H₂CO₃

Dissociation/ ionization

The process by which ions are formed and separate when a compound dissolves in and reacts with water

pH

• H⁺(aq) concentration

• Measure of how acidic/alkaline some thing is (1-14)

• (sf. start after decimal point)

pOH

the hydroxide ion concentration

Neutralization reaction

acid + base → salt + water

Dissociation reaction

Breaking into separate components (with water usually)

Incomplete dissociation

Not all compounds break apart

Hydroxide ion

OH-

Hydronuim ion

H₃O⁺

Polyprotic

Acids/Bases that can donate/Accept more than 1 proton

Oxidation/redox reaction

transfer of electrons between two species

Amphoteric

A substance that can act as both an acid and a base

Amphiprotic

A substance that can act as both a proton acceptor and a proton donor

Bronsted-Lowry

Acids and bases are proton donors or acceptors

Arrhenious

Acid and bases increase concentration of hydrogen ion or hydroxide ion

Autoionization of water

H20(aq)<->H+(aq) + OH-(aq)

Estrification

A carboxylic acid (ROOH) reacts with an alcohol to form an ester.

Precipitation

Formation of a solid during a chemical reaction

Dissolution

A solute in a gaseous, liquid, or solid phase dissolves in a solvent to form a solution

Saturated solution

Has highest possible concentration of solute under given conditions

Determination of pH

1. Acid-base indicators

2. pH meter

3. "Universal" indicator

Corrosive

Chemically reactive

Concentrated

High number of moles of solute per dm³ of solution

Dilute

Low number of moles of solute per litre of solution

Synthesis

Production of chemical compounds by reaction from simpler materials

Decomposition

Breaking down a chemical compound into simpler substances

Reagents

Compound or mixture used to detect the presence or absence of another substance

e.g. by a color change

Anhydrous

A substance containing no water