Acids, Bases, and Salts

Matter Classification

• Matter can be pure or a mixture (impure)
• Mixtures are either homogeneous or heterogeneous
• Pure substances are classified as elements or compounds
• Elements combine in fixed proportions to form compounds
• Compounds are classified into salts, acids and bases
• Examples of elements are hydrogen, iron and chlorine
• Water (H2O) is an example of a compound

Acids

• Acids are sour in taste
• Acids release H+ ions in an aqueous medium based on the Arrhenius theory

Bases

• Bases taste bitter and feel slippery (soapy) to the touch
• Bases release hydroxide ions (OH-) in an aqueous medium (Arrhenius theory)

Salts

• Salts can be acidic, basic, or neutral, depending on the strength of the reacting acid and base
• Salts form through a neutralization reaction between an acid and a base, producing salt and water
• Neutral salts form when strong acids and strong bases react, neutralizing each other completely

Acidic Salts

• Acidic salts form when a strong acid overpowers a weak base, leaving some acidic properties in the resulting salt

Basic Salts

• Basic salts form when a strong base overpowers a weak acid, resulting in a salt with basic properties

Acid-Base Theories

• Arrhenius theory defines acids/bases based on H+/OH- ions in aqueous solutions
• Other theories include Lewis acid-base theory and Bronsted-Lowry theory
• Arrhenius theory is based on aqueous chemistry

Indicators

• Indicators are chemical substances that change color or smell in the presence of an acid or a base
• Indicators are used in the lab to test for acids and bases, as acids and bases should not be tasted

Litmus Paper

• Red litmus paper turns blue in a basic medium
• Blue litmus paper turns red in an acidic medium

Turmeric

• Turmeric stays yellow in an acidic medium
• Turmeric turns red in a basic medium

China Rose

• China rose turns red in an acidic medium
• China rose turns green in a basic medium

Olfactory Indicators

• Olfactory indicators change their smell in acidic or basic mediums
• Vanilla essence, onion, and clove oil are olfactory indicators
• In acidic conditions, olfactory indicators retain their characteristic smell
• In basic conditions, olfactory indicators lose their smell

Synthetic Indicators

• Phenolphthalein and methyl orange are types of synthetic indicators
• Phenolphthalein yields a pink color in a basic medium
• Phenolphthalein has no color change in an acidic medium
• Methyl orange turns red in an acidic medium
• Methyl orange results in a yellow/orange mix color in a basic medium

Types of Acids (by Strength)

• Strong acids undergo 100% ionization in an aqueous solution
• Examples of strong acids are hydrochloric acid (HCl) and sulfuric acid (H2SO4)
• Weak acids only undergo partial ionization in an aqueous solution
• Examples of Weak acids are acetic acid (CH3COOH) and formic acid (HCOOH)

Types of Acids (by Source)

• Organic acids are extracted from natural sources, such as foods or plants
• Examples of organic acids are acetic acid and oxalic acid
• Inorganic acids are prepared in the lab
• Examples of inorganic acids are sulfuric acid (H2SO4) and nitric acid (HNO3)

Types of Acids (by Concentration)

• A dilute acid contains a low amount of acid in a fixed amount of solvent
• A concentrated acid contains a large amount of acid in a fixed volume of solvent

Types of Acids (by Composition)

• Oxyacids contain oxygen along with hydrogen
• Examples of oxyacids are H2SO4 and HNO3
• Hydracids contain only hydrogen

Types of Acids (by Basicity)

• Basicity refers to the number of ionizable H+ ions per acid molecule
• Total number of hydronium ions (H3O+) per molecule or total number of ionizable H+ ions
• Mono-basic acids have one ionizable H+ ion per molecule
• Di-basic acids have two ionizable H+ ions per molecule
• Tri-basic acids have three ionizable H+ ions per molecule
• HCl is an example of a mono-basic acid
• H2CO3 (carbonic acid) is an example of a di-basic acid
• H3PO4 is an example of a tri-basic acid
• H3PO4 is a tri-basic acid: there are three ionizable hydrogens
• H3PO3 is a di-basic acid: only two hydrogens are ionizable, despite having three hydrogens in the chemical formula
• H3PO3: One hydrogen is bonded directly to the phosphorus atom, making it non-ionizable

Strength of Acids

• Acidic strength increases with more H+ ions released in an aqueous solution
• The degree of ionization measures how much an acid ionizes
• Degree of ionization = (number of acid molecules ionized / total number of acid molecules) x 100
• Strong acids have a degree of ionization above 30%
• Weak acids have a degree of ionization below 30%

Preparation of Acids

• Direct combination (synthesis): Hydrogen + Chlorine -> Hydrochloric Acid
• Acidic oxide in water: SO3 + H20 -> H2SO4
• Oxidation of non-metal: Oxidation of sulfur to produce sulfuric acid
• Salt reaction: React a salt with acid to produce new acid

Chemical Properties of Acids

• Acids react with active metals to produce salt and hydrogen gas
• Acids react with metal oxides to produce salt and water
• Non-metal oxides are generally acidic in nature
• Metal oxides are generally basic in nature
• Metal carbonates and metal bicarbonates are slightly basic in nature
• Metal carbonate or bicarbonate on the reactant side indicates CO2 gas as a product
• Acids react with salts
• Metal carbonates react with acids to produce salt, water, and carbon dioxide gas
• Metal bicarbonates react with acids to produce salt, water, and carbon dioxide gas
• Metal sulfites react with acids to produce salt, water, and sulfur dioxide gas (SO2)
• Metal sulfides react with acids to produce salt and hydrogen sulfide gas (H2S)
• Nitric acid (HNO3) is a strong oxidizing agent, so it is usually not used in reactions with metals, as it converts hydrogen gas to water, except with Mg and Mn, where dilute HNO3 gives hydrogen gas

Type of Bases (by Strength)

• Strong bases undergo maximum ionization and weak bases undergo only partial ionization
• Basic strength depends on the number of hydroxide ions (OH-) in an aqueous medium

Type of Bases (by Concentration)

• Dilute base: contains a smaller amount of base
• Concentrated base has a high amount of base.

Type of Bases (by Acidity)

• Acidity of base: Total ionizable hydroxide ions per base molecule
• Mono-acidic base: One Hydroxide ion released from the aqueous medium
• Di-acidic base: Two Hydroxide ions released per base acid medium
• Tri-acidic base: Three Hydroxide ions released per base acid medium

Preparation of Bases

• Metal + Oxygen -> Metal Oxide (basic)
• Metal + Water -> Metal Hydroxide + Hydrogen Gas
• Metal Oxide + Water -> Metal Hydroxide
• Salt + Base -> Different Base
• FeCL3 Salt gets converted an an insoluble base
• Decomposition of Metal Carbonate (heated) -> produces Metal Oxide + CO2

Chemical Properties of Bases

• Non-Metal Oxide (behave like an acid) + Base (Metal Oxide or Metal Hydroxide)-> Salt + Water
• Salt (in aqueous/alkali medium)-> Different base, such as Zinc Hydroxide

Ammonium Salts

• Ammonium salt + Hydroxide Salt-> Ammonia Gas + Water + Salt

pH Scale

• A pH scale measures the strength in an aqueous solution
• The pH scale ranges from 0 to 14
• 7 indicates neutral
• Values less than 7 indicate acidity (lower values are more acidic)
• Values greater than 7 indicate alkalinity/basicity (higher values are more basic)
• pH means Power of Hydrogen
• pH paper is used with a substance for identification
• If a substance is high in acidity, the strip's color is red
• If a substance is neutral, the strip has a green color

The Importance of pH in Everyday Life

• Agriculture: pH of soil is important; highly acidic and basic soil can inhibit plant growth
• Calcium Oxide is used to neutralize soil
• Acid Rain: Results from pollutant gases like carbon, sulfur etc., affecting aquatic animals and structures like marble
• Acid Rain: Rainwater has a pH less than 5.5
• Digestive systems require acids

The Digestive System

• The body requires an acidic medium, using HCL
• The body requires HCL for enzyme activation
• Pepsinogen requires HCL for enzyme action

Self Defense (Animal (Bee's))

• Bee stings inject formic acid into the skin's surface

Decaying teeth

• Tooth decay can occur if mouth pH is < 5.5

Salts

• Salts are ionic compounds formed by complete/partial replacement of ionizable hydrogen atoms of an acid by a metallic ion
• Metallic ions replace ionizable H+ to create salt when aqueous or heat is applied

Types of classification of salts

• Normal salts (formed by acidic neutralization)
• Acidic salts
• Basic salts

The process of classification of salts

• A normal salt results from complete replacement
• An Acidic salt results from partial replacement
• A Basic salt results when the acids are overpowered

Other key points of Salts

• Normal-Neutralization occurs where NaOH + HCL yields NaCl + H20
• Examples of acids in Acid Rain: H2S, HCL

Preperation of Salts

• Direct combination
• Simple Replacement
• Decomposition

Properties of a salt

• Good conductors of electricity in an aqueous state
• Non-volatile
• Exhibit polarity
• Can be acidic or basic

Water or crystal properties

• Some salts like CuSO4.5H20 exhibit crystal properties as hydrated salts

The 3 states(properties)

• Efflorescent
• Hygroscopic
• Deliquescent

Elforesecent Subtances

• Water is lost in a partially way

Hydroscopic Subtatnces

• Absorb moisture from the atmosphere, and may dissolve

Deliquescent Substances

• Does not absorb water

Drying Agents

• Consist of sulfuric acids that remove water molecules from combine state