CHEMISTRY FORM 2
- 1.1 Structure of the atom
- 1.2 Atomic Number and Mass Number
- 1.3 Isotopes
- 1.4 Energy levels and electron arrangement
- 1.5 Development of the Periodic Table
- 1.6 Relative Atomic Mass and Isotopes
- 1.7 Ion Formation
- 1.8 Chemical Formulae
- 1.9 Chemical Equations
- 2.1 Alkali metals (Group I elements)
- 2.2 Alkali Earth Metals (Group II elements)
- 2.3 Halogens (Group VII elements)
- 2.4 Noble gases (Group VIII elements)
- 2.5 Properties and Trends Across the Periodic Table
- 3.1 Bond
- 3.2 Ionic bond
- 3.3 Giant ionic structure
- 3.4 Covalent bond
- 3.5 Co-ordinate bond
- 3.6 Molecular structures
- 3.7 Giant covalent structures
- 3.8 Metallic Bond
- 3.9 Types of bond across a period
- 3.10 Oxides of elements in Period 3
- 3.11 Chlorides of Period 3 elements
- 4.1 What is a salt?
- 4.2 Types of salt
- 4.3 Solubility of salts in water
- 4.4 Methods of preparing salts
- 4.4.1 Reacting a Metal with an Acid
- 4.4.2 Reacting an Acid with a Base (Neutralization)
- 4.4.3 Reacting an Acid with a Carbonate (or hydrogencarbonate of metal)
- 4.4.4 Combining elements Directly (Direct Combination of elements)
- 4.4.5 Precipitation (Double decomposition)
- 4.5 Action of heat on salts
- 4.6 Uses of salts
- 5.1 Electrical conduction
- 5.2 Electrical conductivity of molten substances
- 5.3 Electrical conductivity of substances in aqueous state
- 5.4 Electrolysis
- 5.5 Applications of electrolysis
- 6.1 Allotropes of carbon
- 6.2 Chemical properties of carbon
- 6.3 Carbon (IV) oxide
- 6.4 Carbon (II) oxide (CO)
- 6.5 Large scale production of sodium carbonate and sodium hydrogencarbonate
- 6.6 Effect of carbon (II) oxide and carbon (IV) oxide on the environment
- 6.7 Carbon cycle
Carbon and some of its compounds: Carbon (II) oxide
6.0 Carbon and some of its compounds
6.4 Carbon (II) oxide (CO)
Carbon (II) oxide is both poisonous and useful.
6.4.1 Preparation and physical properties of carbon (II) oxide
Figure 6.4 Set-up to prepare carbon (II) oxide
Sulphuric acid dehydrates methanoic acid (HCOOH). That is, it removes the elements of water (H and O) from methanoic acid. Otherwise, normally, acids do not react with each other.
The gas (CO) is collected over water. It is slightly less dense than air.
2. An alternative method uses oxalic acid (H2C2O4) instead of methanoic acid. But in that case, carbon (IV) oxide is also produced.
3. The gas (CO) can also be obtain by passing carbon (IV) oxide over hot carbon.
C(s) + CO2(g) ⟶ 2CO(g)
- How can we dry carbon (II) oxide?
- If oxalic acid is used, how can carbon (IV) oxide be removed?
- Explain how you would collect dry carbon (II) oxide.
- Draw a labelled diagram for the arrangement you would use to prepare and collect a wet sample of carbon (II) oxide from carbon (IV) oxide and carbon.
- Explain what would be observed when a few drops of concentrated sulphuric acid are added to copper (II) sulphate crystals
Answers to Questions 6.4.1a
How can we know whether a gas is denser or less dense than air?
We have learnt about relative atomic mass (Topic 1). If we can remember that H=1, N=14, O=16, C=12, Cl=35.5 and S=32, we should be able to answer this question. Air consists mainly of nitrogen (N2 = 28) and oxygen (O2 = 32). So the average mass is about 30, but slightly less (about 29) because nitrogen is much more abundant (78%).
Example: Let us find out if methane (CH4) gas is denser or less dense than air.
R.A.M of methane = 12 + (1x4) = 16. This is far less than 30; so methane is less dense than air.
Chemistry in the charcoal burner
Observe the video showing the burning of charcoal in a jiko.
(courtesy Youtube-charcoal flame by Joseph Rabari)
- Just like in the gas burners, fresh air (rich in oxygen) flows by convection from the base of the burner upwards. Charcoal at the bottom therefore receives the most oxygen and completely burns to form product P. Name P. Write an equation for the burning of charcoal at this point.
- Roughly mid-way up, there is hot charcoal but little oxygen; so P shares its oxygen with the hot carbon to form product Q. What is Q? Write a balanced equation for the reaction.
- The flame at the top is blue. Explain this, and write an equation to represent the reaction.
Answers to Questions 6.4.1b
6.4.2 Reactions of carbon (II) oxide
Observe the burning of carbon (II) oxide in air.
(courtesy Youtube-Preparation & Properties of Carbon monoxide by Shiva Chemist)
Answers to Questions 6.4.2
In the reactions with metal oxides, metals lose oxygen to carbon (II) oxide which becomes carbon (IV) oxide. That is, the metal is reduced, while carbon (II) oxide is oxidized. Through such reactions, carbon (II) oxide is used in the extraction of metals from their oxides.