Acids
Definition
An acid is a substance that donates protons (H+ ions) when dissolved in water. Acids are characterized by their ability to change the color of indicators (for example, turning blue litmus paper red) and by having low pH values.
Types of Acids
Acids are classified into two main groups:
- Organic Acids: For example, Acetic acid (CH3COOH), Citric acid (C6H8O7), Formic acid (HCOOH)
- Inorganic Acids: For example, Hydrochloric acid (HCl), Sulfuric acid (H2SO4), Nitric acid (HNO3), Phosphoric acid (H3PO4)
Physical Properties of Acids
- Sour taste
- Water solubility
- Low pH values (typically less than 7)
- Corrosive nature
- Conduct electricity in aqueous solution due to free ions
- May be colorless or colored depending on the acid
- Often volatile in concentrated form
- Density often higher than water
- May emit fumes in air (especially strong acids)
- Reactive with metals and organic substances
Chemical Properties of Acids
- React with metals to produce hydrogen gas (e.g., Zn + 2HCl → ZnCl2 + H2)
- Neutralize bases to form salts and water (e.g., HCl + NaOH → NaCl + H2O)
- React with carbonates to produce carbon dioxide (e.g., CaCO3 + 2HCl → CaCl2 + CO2 + H2O)
- Act as oxidizing agents in some reactions
- Exhibit dissociation (complete for strong acids, partial for weak acids)
- Form conjugate bases upon donating a proton
- Participate in esterification reactions with alcohols
- Catalyze various organic reactions
- Can react with indicators to produce distinct color changes
- May combine with bases to form buffer solutions
Laboratory Tests for Acids
- Blue litmus paper turns red
- Measurement of pH values using pH meters (typically below 7)
- Titration with a standard base to determine acid concentration
- Observation of effervescence when reacting with carbonates
Uses of Acids
- Manufacturing fertilizers (e.g., sulfuric acid in phosphate fertilizers)
- Production of industrial chemicals
- Food industry applications (e.g., acetic acid in vinegar, citric acid as a preservative)
- Battery acid in lead-acid batteries
- Cleaning agents and descaling products
- Laboratory reagents for various chemical syntheses
- pH adjustment in water treatment processes
Bases
Definition
A base is a substance that accepts protons (H+ ions) or produces hydroxide (OH-) ions when dissolved in water. Bases are characterized by their bitter taste, slippery or soapy feel, and by having high pH values.
Types of Bases
Bases can be classified into organic and inorganic types:
- Inorganic Bases: For example, Sodium hydroxide (NaOH), Potassium hydroxide (KOH), Calcium hydroxide (Ca(OH)2)
- Organic Bases: Many organic compounds with amine groups act as bases, for example, Methylamine (CH3NH2) and Aniline (C6H5NH2); note that ammonia (NH3) is often considered a weak base.
Physical Properties of Bases
- Bitter taste
- Slippery or soapy feel
- High pH values (typically greater than 7)
- Water solubility
- Conduct electricity in solution due to free ions
- May be corrosive in concentrated forms
- Generally colorless or lightly colored
- Often higher density in concentrated solutions
- React with organic matter
- Form salts upon neutralization with acids
Chemical Properties of Bases
- Neutralize acids to form salts and water (e.g., NaOH + HCl → NaCl + H2O)
- React with oils and fats to form soap (saponification)
- Accept protons to form their conjugate acids
- Exhibit variable strength based on ionization (strong or weak bases)
- Turn red litmus paper blue
- Participate in complex formation reactions with metal ions
- Can be used as buffering agents in solution
- May catalyze certain organic reactions
- React with acidic gases (e.g., CO2) to form carbonates
- Exhibit thermal stability in some cases
Laboratory Tests for Bases
- Red litmus paper turns blue
- Measurement of pH values using pH meters (typically above 7)
- Titration with a standard acid to determine base concentration
- Observation of a slippery, soapy feel
Uses of Bases
- Manufacture of soaps and detergents
- Cleaning agents for household and industrial use
- Applications in paper production and textile processing
- Water treatment and pH adjustment
- Production of various chemicals
- Neutralizing acidic waste in industrial processes
- Laboratory reagents in chemical synthesis
Salts
Definition
Salts are ionic compounds formed from the neutralization reaction between an acid and a base. They consist of positive ions (cations) and negative ions (anions) held together by ionic bonds.
Types of Salts
- Neutral Salts: Formed from a strong acid and a strong base (e.g., NaCl)
- Acidic Salts: Formed when a strong acid reacts with a weak base (e.g., NH4Cl)
- Basic Salts: Formed when a weak acid reacts with a strong base (e.g., Na2CO3)
Physical Properties of Salts
- Crystalline structure
- High melting and boiling points
- Often soluble in water (varies with salt)
- Conduct electricity in molten state or when dissolved in water
- Generally hard and brittle
- Can be colorless or colored depending on impurities
- Recrystallization upon evaporation of water
- Ability to form hydrates with water molecules
- Variable density
- Stable at room temperature
Chemical Properties of Salts
- Undergo hydrolysis in water, affecting the pH of the solution
- React with acids or bases to produce other salts
- May decompose upon heating (thermal decomposition)
- Undergo ion exchange reactions
- Exhibit electrolysis in molten form or aqueous solution
Laboratory Tests for Salts
- Conductivity tests in solution
- Observation of crystalline structure under a microscope
- Recrystallization experiments
Uses of Salts
- Food seasoning and preservation (for example, NaCl is used as table salt)
- Fertilizers and soil conditioners
- Chemical manufacturing and processing
- Water softening and treatment
- Industrial applications such as glass production
- Electrolysis for extracting metals
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