Essential Chemistry Concepts and Industrial Processes

Fundamental Chemical Principles

Reactivity Trends in Groups I and VII

• Group I (Alkali Metals): Reactivity increases down the group.
  • Their atoms lose their outer electron to achieve a stable electron shell.
  • As the number of electron shells increases, the outer electron is further from the positive nucleus, making it easier to lose.
• Group VII (Halogens): Reactivity decreases down the group.
  • Their atoms gain or share an electron to achieve a stable electron shell.
  • The positive nucleus of the atom attracts the extra electron.
  • As the number of electron shells increases, the outer shell is further from the nucleus, making it more difficult to attract an electron.

Common Ores and Alloys

• Iron Ore: Hematite
• Aluminum Ore: Bauxite
• Sodium Ore: Rock Salt
• Lead Ore: Galena
• Zinc Alloy: Brass (used in musical instruments, locks, keys)
• Stainless Steel: An alloy of Nickel and Chromium, known for being rustproof.

Key Substances and Environmental Impacts

• Carbon Monoxide (CO): Causes oxygen starvation.
• Sulfur Dioxide (SO₂): Contributes to acid rain.
• Nitrogen Oxides (NO_x): Also contribute to acid rain.
• Catalytic Converters: Used to convert harmful CO and NO_x into less harmful gases.

Water Chemistry and Properties

Detecting Water

Two common methods to detect the presence of water:

• Anhydrous Copper(II) Sulfate: Changes from white to blue in the presence of water, forming hydrated copper(II) sulfate.

  CuSO4 + 5H2O = CuSO4•5H2O

• Cobalt(II) Chloride Paper: Changes from blue to pink in the presence of water.

  CoCl2 + 6H2O = CoCl2•6H2O

Water Hardness and Softening

• Temporary Hard Water: Can be softened by boiling. This removes dissolved calcium hydrogen carbonate.

  H2CO3(aq) + CaCO3(s) → Ca(HCO3)2(aq)

• Permanent Hard Water: Remains hard even when boiled. It is typically softened by adding sodium carbonate.

  Ca2+(aq) + Na2CO3(aq) → CaCO3(s) + 2Na+(aq)

Corrosion Protection Methods

Sacrificial Protection

This method involves connecting a more reactive metal (e.g., zinc) to the metal being protected (e.g., iron). The more reactive metal corrodes preferentially, sacrificing itself to protect the other metal.

Example reaction for zinc sacrificial protection:

2Zn(s) + O2(g) + 2H2O(l) → 2Zn(OH)2(aq)

Galvanizing

Galvanizing involves dipping iron or steel into a tub of molten zinc. The resulting thin layer of zinc slowly corrodes away, losing electrons to the iron and thereby protecting it from rust.

Industrial Chemical Processes

Blast Furnace Operation

The blast furnace is used to extract iron from its ore. Impure molten iron from the furnace is then converted into steel by using oxygen to remove impurities.

Fractional Distillation of Air

This process separates components of air, primarily oxygen and nitrogen, based on their different boiling points.

1. Dust and solid impurities (like water vapor and CO₂) are removed from the air.
2. The air is compressed.
3. The compressed air is passed through a jet and allowed to expand rapidly, causing it to cool significantly.
4. The air liquefies due to the extreme cooling.
5. The liquid gases are then stored in tanks and separated by fractional distillation.

Ammonia Production Reaction

Ammonia can be produced in the laboratory by heating an ammonium salt with a strong base, such as calcium hydroxide:

2NH4Cl + Ca(OH)2 → CaCl2 + 2H2O + 2NH3

The Contact Process for Sulfuric Acid

The Contact Process is the industrial method for producing sulfuric acid (H₂SO₄).

1. Sulfur is burned in air to produce sulfur dioxide:

   S + O2 → SO2

2. Sulfur dioxide is mixed with more air and passed over a catalyst (vanadium(V) oxide, V₂O₅) in four separated beds to produce sulfur trioxide. This reaction is exothermic (gives out heat).

   2SO2 + O2 → 2SO3

3. Sulfur trioxide is absorbed into concentrated sulfuric acid to form oleum (disulfuric acid):

   H2SO4 + SO3 → H2S2O7

4. Oleum is then carefully diluted with water to produce sulfuric acid:

   H2S2O7 + H2O → 2H2SO4

Key Chemical Reactions

Biological Processes

• Photosynthesis: The process by which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll.

  6CO2 + 6H2O → C6H12O6 + 6O2

  Oxygen produced can dissolve in the ocean and be utilized by aquatic organisms.

• Respiration: The process in living organisms involving the production of energy, typically with the intake of oxygen and the release of carbon dioxide and water.

  C6H12O6 → 6CO2 + 6H2O + Energy

Combustion Reactions

• Complete Combustion (e.g., Methane): Occurs with sufficient oxygen, producing carbon dioxide and water.

  CH4 + 2O2 → CO2 + 2H2O + Energy

• Incomplete Combustion (e.g., Methane): Occurs with insufficient oxygen, producing carbon monoxide (or soot) and water.

  2CH4 + 3O2 → 2CO + 4H2O

Limestone and its Derivatives

• Thermal Decomposition of Limestone (Calcium Carbonate):

  CaCO3(s) → CaO(s) + CO2(g)

  Calcium Carbonate (Limestone): CaCO₃

  Calcium Oxide (Quicklime): CaO (formed by heating limestone)

  Calcium Hydroxide (Slaked Lime): Ca(OH)₂ (formed by adding water to quicklime)