chem

• why is petrol considered to be a fuel?

  A fuel is a subtance with stored energy that can be released relatively easily for use as heat or power. Petrol primarily contains octane; when octane undergoes complete combustion it releases 47.9 kJ/g.
• What is the difference between a renewable and non-renewable fuel?

  A non-renewable fuel such as coal, oil and natural gas takes millions of years to produce and are used at a greater rate than they can be replaced. A renewable fuel such as biodiesel, bioethanol and biogas are derived from natural plant or animal resources such as sugarcan or cow manure or vegetable oils or waste and can be produced in a short period of time e.g. days/weeks/months. Renewable fuels can be produced at a greater rate than them being used and are sustainable.
• Australia is the fifth biggest producer of coal. Explain which form of coal would you choose between brown or black coal.

  Since brown coal contains a higher H2O content, then the heat energy produced via combustion is used to vaporise the H2O, lowering the overall heat released per mass of fuel. Although black coal is a better fuel choice than brown coal, the disadvantage is that black coal has to be mined further underground than brown coal, thus requiring equipment that can drill longer distances and higher pressures. Brown coal would be chosen because of its availability and accessibility
• Crude oil is mainly a mixture of alkanes, which are separated using a heating process called fractional distillation.
• The alkanes are separated according to their boiling points and strength of dispersion forces.
• Bubble caps stop the upward movement of the gases and the vapors condense into liquid and are collected on trays.
• The alkanes of similar boiling points and containing similar strength of dispersion forces are collected as fractions on each level of the fractionating column.
• As the crude oil mixture is heated at the bottom of the column, then the temperature decreases from the bottom to the top; hence heavy alkanes such as C20 are collected at the bottom and very light alkanes such as C1-C4 are collected at the top of the column.
• what are slc conditions?

  • 100kPa
  • 25 degrees celsius
  • solutions concentration: 1M
• what are limitations of the electrochemical series?

  • doesn't tell you about the rate of reaction - reaction could be occuring very slowly but you can't tell
  • is only based on reactions occurring at SLC