Non-Metals

Prepared December 2007

Alrick Moodie

What are non-metals ?

• Non-metals are those substances which are not metals i.e. they do not ionize by electron loss and do not show the characteristics of metals

Properties of Non-Metals

• Poor conductors of heat and electricity

• Brittle , not malleable and ductile

• Dull in colour

• Low in sonority

Chemical Properties

• React with air/oxygen to give covalent acidic oxides ( although a few give neutral oxides e.g. CO )

• React with metals to form ionic compounds

• Do not react with dilute acids

• Do not react with water except chlorine

• Tend to be oxidizing agents

Common Non-metals

We will be looking at :

• Hydrogen

• Chlorine

• Oxygen

• Carbon

• Sulphur

• Nitrogen

Hydrogen

It is a diatomic gas H2

It is colourless and odourless . It is almost insoluble in water and is the lightest known substance .

Chemical Properties of Hydrogen

• It has a neutral pH

• It burns in air/oxygen

• It combines with reactive metals to give hydrides : Mg + H2 MgH2

• It can act as a reducing agents e.g. in the extraction of metals

CuO + H2 Cu + H2O

Uses of Hydrogen

• Manufacture of ammonia , nitric acid and nylon

• Manufacture of margarine and other hydrogenated oils

• In welding

• As fuel

Laboratory Preparation

• Hydrogen can be prepared by reacting an acid with a metal

Zn + 2HCl ZnCl2 + H2

Diagram of the Laboratory Preparation of Hydrogen

The Water Cycle

Water vapour in the atmosphere condenses and form water droplets and precipitation occurs . If temperature is low we will get snow or hail ( ice ) .

The water on the ground :

• percolates and go underground

• runs off into rivers and the seas

• evaporates

Plants absorb water and loses it through a process called transpiration

Animals also intake water and lose through excretion ( sweat , urine or breathing )

Uses of water

• Domestic purposes e.g. drinking , washing , cooking , cleaning

• Irrigation of crops

• Generation of electricity

• Industrial processes

• Recreational activities

WATER VAPOUR IN AIR

GROUND WATER

DOMESTIC & INDUSTRIALPROCESSES

UNDERGROUND WATER

SEAS

PLANTS

ANIMALS

PRECIPITATION

PERCOLATION

RUN OFF

EVAPOURATION

FEEDING

EXCRETION

TRANSPIRATION

ABSORPTION

DRINKING

EVAPOURATION

Chlorine

Chlorine

It is a diatomic gas Cl2It is a greenish-yellow gas with a choking odour . It is more dense than air and is slightly soluble in water .

Chemical Properties of Chlorine

• Readily combines with metals to form chlorides : Mg + Cl2 MgCl2

• It is a powerful oxidizing agent

• It bleaches substances ( in the presence of moisture )

Uses of Chlorine

• Manufacture of plastics e.g. PVC

• Sterilize water e.g. drinking supplies , swimming pools

• Preparation of cleaning fluids and bleaching agents

• Manufacture of hydrochloric acid

Laboratory Preparation

• Chlorine can be the oxidation of conc. Hydrochloric acid by potassium manganate VII

HCl (l) + KMnO4(s)

KCl (aq) + MnCl2 (aq) + H2O (l) + Cl2 (g)

Oxygen

Oxygen is the most abundant element on Earth . Approximately 50% of the earth’s crust is composed of oxygen containing compounds , while 20% of the atmosphere is free oxygen gas .

Oxygen is a diatomic gas O2 although in the upper atmosphere it exists in the allotrope form as ozone O3 .

It is a colourless odourless gas which is slightly soluble in water and has the same density as air .

Chemical Properties

• It has a neutral pH of 7

• Supports combustion

• Combines with most elements to form oxides

• It is involved in biological processes of respiration .

Uses of Oxygen

• In welding apparatus

• Rocket fuels

• Steel manufacture

• Breathing equipment

Laboratory Preparation

Oxygen is prepared by the catalytic decomposition of hydrogen peroxide .

2H2O2 (aq) 2H2O (l) + O2 (g)

MnO2 is the catalyst used

Carbon

Carbon exists as many natural occurring allotropes ; diamond , graphite , charcoal and coke .

Chemical Properties of Carbon

• Readily burns in oxygen to form carbon dioxide . In limited supply of air carbon monoxide is formed .

• It is a powerful reducing agent at high temperatures .

Carbon Dioxide

Carbon dioxide is a colourless , odourless gas which is slightly soluble in water .

It is more dense than air and is slightly acidic .

The presence of carbon dioxide can be determined by the formation of a precipitate with calcium hydroxide .

Preparation

Carbon dioxide is prepared by the reaction of a carbonate and a dilute acid .

Uses of Carbon dioxide

• As a refrigerant

• As a fire suppressant

• In sodas

Carbon cycle

Sulphur

Sulphur is found in the earth’s crust as a free element and as sulphides and sulphates .

The free sulphur occurs as two allotropes , monoclinic and rhombic .

Chemical Properties

• Burns in air to form sulphur dioxide

• Combines with most metals to form sulphides .

Uses

• Manufacture of sulphuric acid

• Manufacture of gunpowder and matches

• Manufacture of fungicides and pesticides

• Vulcanization of rubber

Sulphur is obtained by the Frasch process where the sulphur is mined directly from the earth in its elemental form .

Sulphuric acid

Concentrated sulphuric acid is a colourless , odourless , oily liquid . It is a powerful dehydrating liquid .

Diluting conc. sulphuric acid is a very exothermic reaction and must be done cautiously .

Uses

• Manufacture of fertilizers

• Manufacture of white paint

• Manufacture of soaps and detergents

• Refining of petroleum

• Vulcanization

Manufacture

Sulphuric acid is manufactured by the Contact process which has three stages .

1. Sulphur is burned in air to form sulphur dioxide S (s) + O2 (g) SO2 (g)

2. The sulphur dioxide is oxidized to sulphur trioxide

2SO2 (g) + O2 (g) 2SO3 (g)

3. The sulphur trioxide is dissolved in concentrated sulphuric acid to form oleum which is diluted to form sulphuric acid .

H2SO4 (aq) + SO3 (g) H2S2O7 (l)

H2S2O7 (l) + H2O (l) 2H2SO4 (aq)

Nitrogen

Nitrogen forms 78% of the air by volume . It is a colourless , odourless gas which is insoluble in water and has the same density as air .

Nitrogen is notoriously inert . However it will combine with oxygen at high temperatures to form nitrous oxides . This occurs during lightning discharges and in the engines of vehicles .

It will also combine with hydrogen under certain conditions of temperature and pressure to form ammonia .

Uses & Manufacture

• As a refrigerant

• As an inert atmosphere in packaging

• Manufacture of ammonia

Nitrogen is obtained by fractional distillation of air .

Ammonia

Ammonia is a colourless gas with a pungent , choking smell . It is less dense than air and is very soluble in water .

Chemical formula NH3

Dissolved ammonia is called aqueous ammonia NH3 (aq) or ammonium hydroxide NH4OH

Chemical properties

• Dissolves in water to give a weakly alkali solution . It is the only common alkali gas .

• Combines directly with acids to form ammonium salts

• Acts as a reducing agent

Laboratory Preparation

Ammonia can be prepared by heating an ammonium salt with an alkali .

2NH4Cl (s) + Ca(OH)2 (s)

2NH3 (g) + CaCl2 (aq) + 2H2O (l)

Industrial Preparation

Ammonia is prepared by the Haber Process . Purified Nitrogen and Hydrogen gases are passed over a finely divided iron catalyst at 350 – 400 oC and a pressure of 250 to 300 atmospheres .

N2 (g) + 3H2 (g) 2NH3 (g)

Uses of Ammonia

• Water purification

• Cleaning agent

• Refrigerant

• Manufacture of fertilizers

• Manufacture of nitric acid

• Manufacture of nylon

Gas Colour Odour Test

Hydrogen None None Gives a pop with a lighted splint .No effect on litmus

Oxygen None None Relights a glowing splint .No effect on litmus

Carbon dioxide None None Turns lime water cloudy then colourless

Ammonia None Pungent Dense white fumes formed when in contact with hydrogen chloride .

Turns moist red litmus blue .

Sulphur dioxide None Choking Reduces potassium dichromate and manganate VIITurns moist blue litmus red .

Hydrogen chloride

None Irritating Dense white fumes formed when in contact with ammonia .

Turns moist blue litmus red .

Chlorine Yellow-green Irritating Moist blue litmus turns red and then bleached .

Nitrogen dioxide

Brown Irritating Moist blue litmus turns red .

Water vapour None None Cobalt chloride paper turns from blue to pink .