Lewis Structure of Oxygen

Oxygen

Lewis structure of oxygen

Preparation of Oxygen

a. Thermal decomposition of potassium chlorate(V)

2 KClO3 ( s )  2 KCl ( s ) + 3O2 ( g ) →

Drying agent: CaCl2, CaO, concentrated H2SO4

heat ,300ο C MnO2

b. Catalytic decomposition of hydrogen peroxide solution

2 H 2O2 (aq)  2 H 2O(l ) + O2 ( g ) →

c. Reaction between sodium peroxide and water 2Na2O2(s) + 2 H2O (l) → 4NaOH (aq) + O2 (aq)

MnO2

Other substances that produce O2

2 F2 ( g ) + 2 H 2O(l )  4 HF (aq) + 2O2 ( g ) → 2 HClO(aq) → 2 HCl (aq) + O2 ( g )

heat 2 KNO3 ( s ) → 2 KNO2 ( s ) + O2 ( g )  sunlight

2 AgNO3 ( s ) → 2 Ag ( s ) + 2 NO2 ( g ) + O2 ( g ) 

heat

Industrial Preparation

a. electrolysis of water and molten sodium hydroxide .

2 H 2 O ( l )  electro lysis → H 2 ( g ) + O 2 ( g )  2 N a O H ( l )  electro lysis → 2 N a ( s ) + H 2 ( g ) + O 2 ( g ) 

b. fractional distillation of liquid air.

Physical Properties

• • • • Oxygen is a diatomic gas. colorless, odorless and tasteless neutral to moist litmus paper. slightly soluble in water, i.e. only about 2% by volume of it will dissolve at room temperature. • denser than air. • Gaseous oxygen liquefies at −183°C (b.p) and solidifies at −225°C (m.p)

The Term Paper on Combustion Carbon Dioxide Oxygen Heat Gas

... only needs an atmosphere with at least 16 percent oxygen. Heat is the energy necessary to increase the temperature of the ... live and grow. Green plants convert carbon dioxide and water into food and oxygen. Plants and animals, in turn, "burn" the food ... hydrocarbons burn to produce equal amounts of carbon dioxide and water, the one releasing more energy is less stable, since it ...

Chemical Properties

• very reactive. • combines readily with all other elements (except the noble gases, some halogens and some un-reactive metals) to form oxides.

Reaction with metals

• Many metals react with oxygen to form basic oxides(contains the O2- ion).

• Example: • 2 Cu (s) + O2 (g) → 2 CuO (s) • 2 Mg (s) + O2 (g) → 2MgO(s)

Reaction between alkali metals and oxygen

• The basic oxide is not formed when sodium or potassium is heated in a plentiful supply of oxygen. − • Metal peroxides (contains O22− ion) are formed. • Sodium burns with a bright yellow flame to form sodium peroxide, Na2O2. 2Na(s) + O2 (g) → Na2O2(s) (sodium peroxide) Oxidation state of oxygen in peroxides is −1.

superoxides

• Very reactive alkali metals -K, Rb and Cs can also form superoxides (O2− ion) • Potassium burns in excess oxygen with a lilac flame to form a higher oxide, KO2 . • K(s) + O2 (g) → KO2 (s) (potassium superoxide) • Oxidation state of oxygen in superoxides is

1 − 2

nonReaction with non-metals

• Nonmetals burn in oxygen to form acidic oxides. • Example: 1 S (s) + O2 (g) → SO2 (g) 2 P4 (s) + 3 O2 (g) → P4O6 (s)

Reaction of oxygen with

a. hydrogen sulphide b. Methane c. ammonia

ignited 2 H 2 S ( g ) + 3O2 ( g )  2SO2 ( g ) + 2 H 2O(l ) →

CH 4 ( g ) + 2O2 ( g )  CO2 ( g ) + 2 H 2O(l ) → 4 NH 3 ( g ) + 5O2 ( g )  4 NO( g ) + 6 H 2O(l ) →

pt − Rh ,850ο C

Test for oxygen

• Rekindle a glowing splinter. • Dinitrogen monoxide also does this. • it can be distinguished from oxygen by reactions with NO NO + O2 (g) → NO2 Produces reddish-brown fumes of NO2 • N2O + O2 (g) → No reaction

Classification of Oxides

The Essay on Determination of the amount of dissolved oxygen

Topic : Determination of the amount of dissolved oxygen in a water sample by iodometry-the winkler’s method. Objective: To determine the amount of dissolved oxygen in a water sample by iodometry- the winkler’s method. Apparatus: volumetric pipette, 3 conical flask, burette, burette clamp, Pasteur pipette, reagent bottle, conical flask stopper, retord stand, white tile Materials: 2 ml manganese ...

Basic oxides Metal oxides oxides Nonmetal oxides Acidic oxides Neutral oxides Amphoteric oxides

Basic Oxides

• most metal oxides are ionic compounds. • Example: CaO , BaO, K2O , Na2O …. • dissolve in water to form hydroxides. K2O(s) + H2O(l) → 2KOH (aq) • metallic oxide reacts with acid to produce a salt and water only. MgO(s) + 2HCl(aq) → MgCl2 (aq) + H2O(l)

Acidic oxides

• non-metal oxides are covalent compounds Example: CO2, SO3 , SO2 ,P4O10…. • dissolved in water to give acid • also known as acid anhydrides. • SO2 (g) + H2O(l) → H2SO3 (aq) • SO3 (g) + H2O(l) → H2SO4 (aq) • P4O6 (g) + 6 H2O(l) → 4 H3PO3 (aq) • P4O10 (g) + 6 H2O(l) → 4 H3PO4 (aq)

Amphoteric oxides

• a metallic oxide which can show both basic and acidic properties • can react with both acid and alkali to produce a salt and water only • Example: ZnO , PbO, SnO, Al2O3 , …. • For example, aluminium oxide reacts with hydrochloric acid to form aluminium chloride Al2O3 + 6 HCl → 2 AICl3(aq) + 3 H2O (aq)

Amphoteric oxides with alkali

• aluminium oxide reacts with sodium hydroxide to form sodium aluminate: Al2O3 + 2KOH + 3 H2O → 2 KAI(OH)4 (aq) Or Al2O3 + 2KOH → 2 KAIO2 (aq) + H2O • ZnO + 2NaOH → Na2ZnO2 (aq) + H2O or ZnO + 2 NaOH + H2O → Na2Zn(OH)4 (aq)

Neutral oxides

• shows neither basic nor acidic character. Example: N2O , CO, NO, H2O ….

Peroxides

• Peroxide is a compound with oxygen in the −1 oxidation state. − • Peroxides contain either O22− ion or the covalently bonded group OO. • Example: BaO2 , H2O2 , Na2O2 (pale yellow powder)

Sodium peroxide

• React with cold water or cold dilute acids, it reacts to form hydrogen peroxide. • 2 Na2O2(s) + 2 H2O (l) → 4 NaOH (aq) + O2 (aq) • Na2O2 (s) + H2SO4(aq) → Na2SO4(aq) + H2O2 (aq)

• It is used in air purifiers in submarines and portable breathing apparatus. • it reacts carbon dioxide, forming oxygen and sodium carbonate. 2Na2O2(s) + 2CO2 (g) → 2Na2CO3(s) + O2(g)

Hydrogen Peroxide

Chemical Properties

Thermal decomposition • hydrogen peroxide solution is warmed in a test tube. • Effervescence occurs. The gas is oxygen, but it will not rekindle a glowing splint because of the presence of steam. 2 H2O2 (aq ) → 2 H2O (g) + O2 (g)

The Essay on Oxygen Cycle

The oxygen cycle is the biogeochemical cycle that describes the movement of oxygen within its three main reservoirs: the atmosphere (air), the total content of biological matter within the biosphere (the global sum of all ecosystems), and the lithosphere (Earth’s crust). Failures in the oxygen cycle within the hydrosphere (the combined mass of water found on, under, and over the surface of a ...

preparation

• Reaction between barium peroxide and dilute sulphuric acid. • insoluble barium sulphate(VI) formed is filtered off. BaO2 (s) + H2SO4 (aq) → H2O2 (aq ) + BaSO4 (s)

H2O2 act as an oxidizing agent

• Oxidised lead (II) sulphide PbS (s ) + 4 H2O2 (aq ) → PbSO4 (s) + 4 H2O (l) • This reaction is used in restoring pictures. Hydrogen sulphide in the air reacts with the white lead paint, lead(II) carbonate • lead(II) sulphide, which is brown and makes the picture dingy. • Washing with hydrogen peroxide restores the white colour.

H2O2 act as a reducing agent

• With a stronger oxidising agent , it act as a reducing agent. • Reduces silver oxide Ag2O(s) + H2O2(aq ) →2 Ag(s) + H2O(l)+ O2 (g) Oxygen gas is formed.

Reduces acidified KMnO4

2 MnO4− (aq ) + 5 H2O2 (aq ) + 6 H +(aq ) → 2 Mn2+ (aq ) + 8 H2O (l) + 5 O2 (g) • purple solution decolourised.

Superoxides

• binary compound. • oxidation state of oxygen in superoxides is −½. • dissolve in water to produce oxygen. 4 KO2 (s) + 2H2O (l) → 4 KOH + 3 O2(g) • is used as oxygen source in masks worn for rescue work. • moisture in the breath causes the compound to decompose to form O2 and KOH. The KOH formed will remove CO2 from the exhaled breath. • KOH(s) + CO2 →KHCO3 (s)

The end