Railway Science (Chemistry-Chemical Reaction) (Part-II)

A metal in the combined state has positive valency and a positive ion gets converted into an atom or metal with the addition of an electron(s) called reduction process.
Methods of extracting metals from their ore: Reduction of the ore with carbon, reduction of the molten ore by electrolysis, and reduction of the ore with a more reactive metal.
Carbon reduction method : The oxides of less electropositive metals are reduced by strongly heating them with coal or coke. Carbon combines with the oxygen of the metal oxide to form carbon monoxide which can also act as a reducing agent.

CuCl₂ (Copper(II) chloride) is formed. Metal oxides are usually basic in nature. When they react with acid, products are salt and water.Copper oxide is a weak base while Hydrochloric acid is a strong acid (CuO+ 2HCl → CuCl₂   + H₂O ).
In a neutralization reaction, acid reacts with base to form salt and water. Applications : Wastewater treatment in order to reduce the damage created by the effluents, manufacturing of antacid tablets, to control the pH of the soil.

When carbon monoxide (CO) reacts with hydrogen gas at 340 atm (pressure) it forms methyl alcohol. CO + 2H₂ → CH₃OH. Methanol (methyl alcohol) is a highly versatile chemical commonly used for manufacturing applications and as a fuel for factories and for producing electricity.

BaSO₄ (Barium Sulphate) - Sulphate salt of barium and is found as the mineral barite. Properties - Odorless, white crystalline solid, insoluble in water and alcohol but soluble in concentrated acids.
Uses - casting of copper anode plates as a coating material, radio-opaque agent, component in oil well drilling fluids and increase the density of the polymer by acting as a filler for plastics.

Oxidation is the loss of electrons or an increase in the oxidation state. Oxidising agent - Oxidise other substances and thus increase their oxidation state. Example - Sulphuric acid (H₂SO₄), Potassium nitrate (KNO₃). Oxidation is responsible for the deterioration in the quality of food products, including off-flavors and off-odors.

When dilute sulphuric acid is poured on zinc granules, then zinc being more reactive than hydrogen displaces it from the acid and forms zinc sulphate (ZnSO₄) and hydrogen gas. Zn + H₂SO₄ → ZnSO₄ + H₂ .
Zinc sulphate - Boiling Point (740°C) and Melting Point (680°C). Zinc is important for growth, for body tissue development and health. Hydrogen is a combustible gas and burns with a popping sound.

A precipitation reaction occurs when lead nitrate reacts with potassium iodide. When a solution of potassium iodide is added to a solution of lead nitrate taken in a test tube, the precipitation of a yellowish solid is observed.
This yellowish solid is lead iodide. Potassium nitrate is formed along with lead iodide. This is a double displacement reaction. 2KI(aq .) + Pb (NO₃)₂ (aq .)→2KNO₃ (aq .) + PbI₂(s).

The Chlor-Alkali process is an industrial process for the electrolysis of sodium chloride solution (brine). Reactions - At anode (oxidation):
2Cl⁻ (aq) → Cl₂ (g) + 2e⁻. At cathode (reduction): 2H₂O (l) + 2e⁻ → H₂ (g) + 2OH⁻ . Na+ migrates across the diaphragm to the cathode compartment by combining with OH⁻ to form NaOH.
Overall reaction: 2NaCl (Sodium chloride)(s) + 2H₂O (l) → Cl₂ (g) + H₂ (g) + 2NaOH (sodium hydroxide)(aq).

ZnO (Zinc Oxide) + C → Zn + CO (redox reaction). Zinc oxide is the oxidizing agent as it oxidizes carbon to carbon monoxide. Carbon is a reducing agent as it reduces zinc oxide to zinc.
Zinc - Atomic number (30), Atomic mass (65.38), Discovered by Andreas Marggraf. Properties - density (7.13 g/cm³), melting point (420 °C), boiling point of (907 °C), high heat capacity and heat conductivity.

It is because in the Electrochemical series (ECS) Cu (Copper) comes after Pb (lead), which means Cu cannot displace Pb (lead). The order of ECS is: Li, K, Ba, Ca, Na, Mg, Al, Mn, Zn, Cr, Fe, Co, Ni, Sn, Pb, H, Cu, Hg, Ag, Pt, Au.