2. OXYGEN
the element is very common
highly reactive nonmetallic element
major component of air
the second largest single component of the earth's atmosphere
(21% by volume)
Oxygen is the most abundant element by mass in the Earth‘s
crust as part of oxide compounds such as silicon dioxide.
the atmosphere of Mars contains only about 0.15% oxygen
usually bound with other elements
produced by plants during photosynthesis
necessary for aerobic respiration
3. Properties
• Name: Oxygen
• Symbol: O
• Atomic number: 8
• Atomic weight:
15.9994
• Group number: 16
• Period number: 2
4. Introduction
Phase gas
Melting point -218.79C
Boiling point -182.96C
• freshwater contains about 6.04 milliliters (mL) of oxygen per liter
• Oxygen has vital biological role
•6 CO2 + 6 H2O + photons → C6H12O6 + 6 O2
•C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + 2880 kJ·mol−1
5. Properties
heavier than air
soluble in water
without smell or taste
the gas is colourless, odourless and tasteless
chemical bonds with almost all other elements
three isotopes
6. Property
liquid O2 and solid O2
have a light blue color
highly paramagnetic
Electronegative
highly oxidizing
releasing heat
Liquid oxygen
8. History
• Discovered by: Joseph Priestley, Carl Scheele
• Discovered at: England, Sweden
• Discovered when: 1774
Joseph Priestley
9. Preparation
• large number of different methods for its preparation
1) Preparation of oxygen using potassium chlorate
2 KClO3 ==> 2 KCl + 3 O2
2) Preparation of oxygen using hydrogen peroxide
2 H2O2 ==> 2 H2O + O2
10. Preparation
3) Preparation of oxygen by electrolysis of water
2 H2O ==> 2 H2 + O2
4) Preparation of oxygen by the decomposition of
salts
2 KNO3 ==> 2 KNO2 + O2
5) Preparation of oxygen from air by distillation
11. Compounds
• oxygen is very reactive
• oxygen forms chemical bonds with almost all other
elements
• oxygen derivatives are prone to form free radicals
• the most common oxidation numbers are -1,-2
12. Compounds
Hydroxide
Aluminium hydroxide, Al(OH)3
Barium hydroxide, Ba(OH)2
Oxide
Carbon dioxide, CO2
Water
has the chemical formula H2O
Alcohols (R-OH)
methanol, CH3OH
Methanol burns in air forming carbon dioxide and water:
2CH3OH + 3 O2 → 2CO2 + 4H2O
13. Ozone
allotropic form of oxygen
important component of the atmosphere
effect on the ozone layer
ozone is toxic!
used for drinking water treatment
14. Applications
oxygen is essential to respiration
used in medicine
used in welding and cutting (3,500 °C)
making of steel and methanol
Smelting process
A notable application of O2 as a low-
pressure breathing gas is in modern space suits
and in diving.
