Rev A Feb 2007 Ms. Hennessey

One of the World’s Deadliest

Lake Nyos, Cameroon

Rev Jan 2015 Ms. Hennessey

August 21st 1986- Lake kills 1,700Carbon Dioxide gas killed all living things within a 15-mile (25km)

radius of the lake

Lesson Objectives

To be able to:

• List the physical and chemical properties of CO2

• Describe how to prepare CO2

• Explain the chemical reactions of CO2

• List the uses of CO2

Rev Jan 2015 Ms. Hennessey

Discovery of Carbon Dioxide

Scottish Chemist Joseph Black found that limestone (Calcium Carbonate) could be heated or treated with acids to yield a gas he called "fixed air."

He observed that the fixed air was denser than air and did not support either flame or animal life.

Carbon Dioxide Molecule - Structure

•Carbon dioxide is a chemical compound composed of one carbon and two oxygen atoms.

•It is often referred to by its formula CO2.

•The elements bond by sharing electrons.

C OODouble Covalent Bond

C

CO2

Double Covalent Bond

6P

6N O8P

8NO8P

8N

Oxygen

Carbon

Oxygen

Carbon Dioxide Molecule - Structure

The Preparation of CO2

•Carbon Dioxide is prepared by reacting dilute Hydrochloric Acid (HCl)

with Marble Chips Calcium Carbonate (CaCO3)

CaCO3 + 2HCl → CaCl2 + CO2 + H2O

Rev A Feb 2009 Ms. Hennessey

Preparation of Carbon Dioxide

The Collection of CO2

Carbon Dioxide can be collected using two

methods

•by the upward displacement of air (its denser than air).

Or

•Downward displacement of water (it is only slightly soluble in water)

Physical Properties of CO2

Colourless, Odourless,

Tasteless Gas.

Denser (heavier) than air.

(Density is 1.5 times > air)

Slightly soluble in water

Does not support combustion.

It is an Acidic gas turning blue litmus red.

Turns limewater (Calcium Hydroxide – Ca(OH)2 milky white

It Dissolves in water to form an acid solution (Carbonic Acid – H2CO3)

Chemical Properties of CO2

Tests for Carbon Dioxide

Acidity Combustion Limewater

Turns BlueLitmus Red

Extinguishes a burning Candle

Turns Limewater Milky

Reactions of Carbon Dioxide

Lime water + Carbon Dioxide -> Chalk + water

Ca(OH)2 + CO2 -> CaCO3 + H2O

Water + Carbon Dioxide -> Carbonic Acid

H2O + CO2 -> H2CO3

• It is present in the Earth’s Atmosphere at a low concentration and acts as a Greenhouse gas.

• In its SOLID state, it is called dry ice.

• It is a major component of the Carbon Cycle.

Carbon Dioxide

Photosynthesis

Internal Respiration

Burning

Carbon Cycle

Carbon dioxide in the Air

Green Plants

Internal Respiration

Decay

Animals

Dry Ice

•Solid CO2 is referred to as dry ice and has a number of advantages over common ice– Much colder and can obtain

a temperature of (-78oC)

– It does melt into a liquid by ‘sublimes’ changes from a solid to a gas.

Uses include: - Cooling foods during

transportation- Coolant in nuclear reactors- Special effects on stage.

Uses of Carbon Dioxide

•Photosynthesis – used by green plants to make food (glucose) which is stored in the plant as starch.

•Fire extinguishers

•Carbonation of soft drinks.

Summary

• Colourless, Odourless andTasteless Gas.

• Denser (heavier) than air. (Density is 1.5 times > air)

• Slightly soluble in water

• Important part of the Carbon cycle

• Key molecule in photosynthesis

• Does not support combustion.

• It is an Acidic gas turning blue litmus red.

• Turns limewater (Calcium Hydroxide – Ca(OH)2 milky white

• It Dissolves in water to form an acid solution (Carbonic Acid –

H2CO3)

Rev Jan 2015 Ms. Hennessey