1. Halogens review
What’s the difference between hydrogen chloride and hydrochloric acid?
Why is hydrogen chloride acidic in water but not in methyl benzene?

2. Hydrogen chloride Hydrogen chloride – gas, colourless, strong odour
Hydrochloric acid – is in aqueous solution
Hydrogen chloride reacts with water and forms hydrochloric acid

3. Methyl benzene Water is polar (which means its charged)
Methyl benzene is non polar
The polar water causes the hydrogen chloride to break up into H+ and Cl- ions. (hydrogen chloride is also polar)
Hydrochloric acid is acidic as it as H+ ions

4. Oxygen and oxides

5. Learning outcomes
2.16 recall the gases present in air and their approximate percentage by volume 2.17 describe how experiments involving the reactions of elements such as copper, iron and phosphorus with air can be used to determine the percentage by volume of oxygen in air 2.19 describe the reactions with oxygen in air of magnesium, carbon and sulphur, and the acid- base character of the oxides produced 2.22 recall the properties of carbon dioxide, limited to its solubility and density 2.23 explain the use of carbon dioxide in carbonating drinks and in fire extinguishers, in terms of its solubility and density 2.24 understand that carbon dioxide is a greenhouse gas and may contribute to climate change

6. Air 78% Nitrogen 21% Oxygen 0.93% Argon and other noble gases
0.04% carbon dioxide
Variable amounts of water vapour
Variable amounts of pollutant gases

7. Oxygen Extracted from air by fractional distillation
If air is cooled down, at °C oxygen condenses into a liquid (at -196°C Nitrogen condenses too)

8. Burning magnesium magnesium + oxygen magnesium oxide + reactants
product
magnesium + oxygen magnesium oxide +

9. Heating other metals
Heating copper in air

10. Burning copper
reactants
product
copper + oxygen copper oxide +

11. Copper and air

12. Iron and air

13. The amount the water rises indicates the percentage oxygen in the air
Iron and air
The amount the water rises indicates the percentage oxygen in the air

15. CH4(g) + 2O2(g) CO2(g)+ 2H2O(g)
Methane and oxygen
methane + oxygen carbon dioxide + water
CH4(g) + 2O2(g) CO2(g)+ 2H2O(g)

16. Carbon and oxygen Carbon burns producing carbon dioxide and water
C + O2 CO2 + 2H2O

17. Sulphur dioxide SO2
Produced by burning sulphur (or burning fossil fuels)
S(l) + O2(g) SO2(g)

18. In water
Dissolves to form sulphurous acid
SO2(g) + H2O(l) H2SO3(aq)

19. With an alkali
Forms a sulphite
SO2 + 2NaOH Na2SO3 + H2O

20. Carbon dioxide

21. Preparing carbon dioxide
Acid + carbonate salt + water + carbon dioxide
2HCl + CaCO3 CaCl2 + H2O + CO2

22. In water Dissolves to form carbonic acid CO2(g) + H2O (l) H2CO 3(aq)
pH 5.5

23. In alkali H2CO 3(aq) + 2NaOH(aq) Na2CO3(aq) + 2H2O(l)
acid + base salt + water

24. So what happens when the pressure is released?
Uses of carbon dioxide
Fizzy drinks. The higher the pressure, the more soluble the gas becomes.
So what happens when the pressure is released?

25. Uses of carbon dioxide
Fire extinguishers
How does it work?

26. Uses of carbon dioxide
Dry ice (actually it’s condensed water vapour that you can see.)

27. Oxides of nitrogen
Nitrogen is generally an unreactive gas, and needs fairly extreme conditions to get it to react with oxygen

28. Nitric oxide, NO
Lightning brings about the direct union of nitrogen and oxygen in the air to produce small amounts of nitric oxide, as does the high temperatures produced in car engines.

29. Nitric oxide, NO
It is a toxic air pollutant, often linked with asthma and allergic responses

30. Nitrogen dioxide, NO2
In the presence of excess oxygen, nitric oxide, NO, will be converted to nitrogen dioxide,NO2. Nitrogen Dioxide is a reddish brown, toxic gas at room temperature. NO2 condenses to a brown liquid, but freezes to a colourless solid.

31. Nitrogen dioxide, NO2
Nitrogen Dioxide has been used as a catalyst in certain oxidation reactions; as a nitrating agent for organic compounds; as an oxidizing agent; as a rocket fuel; and as a flour bleaching agent

32. You don’t need to know about this!
Nitrous oxide, N2O
You don’t need to know about this!
Formed when ammonium nitrate, NH4NO3, is heated. A colourless gas with a pleasing odour and sweet taste, is used as an anesthetic for minor operations, especially in dentistry.

33. Nitrous oxide, N2O
It is called laughing gas because of its intoxicating effect. It is also widely used as a propellant in aerosol cans of whipped cream!

34. A reminder!

35. Rusting
Rust is a form of iron oxide. It has water bonded loosely to it. It is called hydrated iron oxide

36. It’s actually the oxygen in air
In order for iron to rust
Both air and water’s a must,
Air alone won’t do
Without water there too,
So protect it, or get a brown crust!
It’s actually the oxygen in air

38. Protecting from rust

39. Protecting from rust Protection method How it works Paint Barrier
Vaseline/oil
Silicone
Zinc (Galvinising)
Sacrificial

40. Sacrificial protection

41. Sacrificial protection
Zinc is electrically connected to the iron. Any water or oxygen reacts with the zinc (or magnesium) instead of the iron. Coating in zinc is called galvanization and it works even when the zinc coating is scratched.