Chemistry Revision (Unit 2: Quantitative and Environmental Chemistry)

Question 1

Explain alkanes

Answer 1

• Type of fuel that is a hydrocarbon
• Compounds composed of single covalently bonded hydrogen and carbon atoms
• Follow formula of CnH2n+2
• Each carbon atoms forms four bonds, one with each hydrogen atom
• Methane, ethane, propane

Question 2

Explain alkenes

Answer 2

• Type of fuel that is a hydrocarbon
• Compounds composed of carbon atoms double covalently bonded to each other, each with 2 hydrogen atoms single-covalently bonded
• Follow formula of CnH2n
• Examples include ethene and propene

Question 3

Explain exothermic and endothermic reactions

Answer 3

• Endothermic reactions are chemical reactions that absorb heat
• Exothermic reactions are chemical reaction that release heat

Question 4

Explain combustion of fuels

Answer 4

• When a fuel reacts with oxygen
• Is an exothermic reaction as it transfers thermal energy to surroundings
• Uses chemical store of fuel to release energy
• Type of oxidation reaction (subtance gains oxygen)

Question 5

Explain air pollution pollutants

Answer 5

Carboon monoxide:
- Produced from incomplete combustion of hydrocarbons due to lack of oxygen
- Considered toxic
- Has high attraction to RBCs as it can fit tightly, preventing them from absorbing oxygen, therefore leading to lower lung capacity

Soot (Carbon particles):
- Produced by incomplete combustioon of hydrocarbons, particularly from diesel engines
- Dirty, lots of dust in atmosphere
- Can lead to global dimming and lcimate change

Carbon dioxide:
- Product by combustion, respiration, and natural processes
- Can lead to global warming

Sulfur oxide:
- Produced from burning coal
- Dissolves in clouds, reacting with water to make sulphurous acid or sulphuric acid, lowering pH below 5.5, causing acid rain

Nitrogen oxides:
- Produced from burning fuel in engines
- Dissolves in water to make nitric acid
- Causes climate change

Question 6

Explain the Haber process

Answer 6

• Makes ammonia
• Uses H2 from methane, nitrogen from air
• Needs to be in 400 degrees celsius, 200 atm, and iron catalyst

1) Gases are mixed and scrubbed
2) Then combressed
3) Then pumped to iron catalyst and converter
4) Pumped into cooler and condensed into liquid ammonia
5) Unreacted H2 and N2 are then pumped again and reacted

Question 7

Explain calorimetry

Answer 7

• The process of measuring heat transfers during a chemical reaction
  1) Measure volume of water and pour it into copper calorimeter
  2) Use thermometer to record initial temperature of water
  3) Heat water up using flame of burning fuel in spirit burner
  4) Record final temperature of water

Measure energy release:
- Use q=Mc(change in T)