P-Block Elements and Their Compounds-II: Group 16 Elements (For CBSE, ICSE, IAS, NET, NRA 2022)

Doorsteptutor material for NTSE/Stage-II-National-Level is prepared by world's top subject experts: get questions, notes, tests, video lectures and more- for all subjects of NTSE/Stage-II-National-Level.

Group 16 Elements

  • Group 16 elements show the usual gradation from non-metallic to metallic properties with increasing atomic number.
  • Oxygen and Sulphur are non-metals, selenium and tellurium are semiconductors and polonium is metallic.
  • Elements can enter into chemical combination and complete their octets by gaining two electrons to form the 2 di-valent ions, e. g. , except polonium which is too metallic.

Properties of Group 16 Element

Properties of Group 16 Element

Occurrence

  • Oxygen occurs in the atmosphere to the extent of about 21 per cent by volume.
  • Element is present in the earth՚s crust and in water to the extent of about 50 per cent and 89 per cent by weight, respectively.

Preparation of Dioxygen

By Heating Chlorates, Nitrates and Permanganates

By Heating Metallic Oxides

By the Action of Bleaching Powder on Hydrogen Peroxide Solution

By the Action of Hot and Concentrated Sulphuric Acid on Potassium Dichromate or Potassium Permanganate

By the Action of Sodium Peroxide on Water

Manufacture of Oxygen

By the Electrolysis of Water

  • The electrolysis is carried out in iron tanks containing a solution of caustic soda or acidified water.
  • The electrodes used are of iron or nickel and a current of 1000 amperes is used.
  • A porous diaphragm is used to prevent the mixing of hydrogen and oxygen.

From Air

  • Barium oxide is heated in air to about 500°C, it combines with oxygen to form barium peroxide, .
  • On raising the temperature to about 800°C, the peroxide decomposes to give barium oxide and oxygen.

(at about 500°C)

(at about 800°C)

Properties

Physical Properties

  • Oxygen is colourless, tasteless and odourless gas and slightly heavier than air.
  • Liquid oxygen is pale blue with boiling point – 182.5°C and specific gravity 1.2386 at – 210°C.
  • It is less soluble in water (about 3 %) , which is responsible for aquatic life.
  • Liquid oxygen is paramagnetic and is strongly attracted by magnet.

Chemical Properties

  • Oxygen is essentially required for the burning or combustion of substances in air.
  • Molecular Oxygen combines directly with most of the elements, exceptions being the inert gases , the halogens, gold and platinum.
  • It is a fairly good oxidising agent in aqueous solution and directly oxidises , , , , and ions.
  • It oxidises some substances at ordinary temperature, some at higher temperatures and some in presence of suitable catalysts.

(at room temperature)

(at high temperature)

Uses

For the Production of High Temperature Flames

  • Oxy-hydrogen flame = 2400° — 2800°C
  • Oxy-coal gas flame = 2200° — 2400°C
  • Oxy-acetylene flame = 3100° — 3300°C

For Medical Purposes

When a patient is unable to breath sufficient air, oxygen is given for artificial respiration.

In Iron and Steel Industry

  • Addition of oxygen to the air blast in blast furnace raises the temperature required for the manufacture of iron and steel.
  • It is also used for bleaching purposes.
  • Oxygen is used as an oxidizing agent in laboratories and in many industries.

Developed by: