Fuels

Question 1

Fractional distillation

Answer 1

involves heating crude oil to diff temps to separate + collect the diff components of the mixture via boiling/condensing points.

Question 2

Calorimetry

Answer 2

method of measuring heat energy released or absorbed by a chemical reaction or physical process, such as combustion of a fuel or food

measures change in temp. of water

Question 3

Limitations of calorimetry

Answer 3

• heat loss to enviro. (biggest source of inaccuracy)
• inaccurate temp recording/volume measurement

Question 4

Energy content

Answer 4

amount of heat (J or kJ) produced upon burning 1g of pure substance

Question 5

Bomb Calorimetry

Answer 5

• sealed ‘bomb’ vessel
• measure heat of combustion of chem reactions
• involve gaseous reactants or products
• high pressures + temps, + maintaining constant volume
• elec circuit –> electrically ignited to start combustion
• needs sufficient oxygen
• water –> heat energy transferred measured
• insulation –> X released into surrounding enviro.
• stirrer –> heat = evenly distributed

Question 6

Solution calorimetry

Answer 6

• in a solution
• measure energy transferred in chem reaction
• polystyrene cup –> constant pressure
• insulated container holds known volume of water –> reaction in solution e.g. dissolution of solid occurs
• temp. surrounding water increases –> exothermic
• temp. surrounding water decreases –> endothermic
• lim. = polystyrene absorbs some heat from water –> change in temp = slightly lower than should be
• lim = combustion can X occur in aq solution
• useful for dissolving substances (e.g. sugar in water), enthalpy changes in acids/bases

Question 7

Increase reliability

Answer 7

Increase repeats

Question 8

Increase accuracy calorimetry

Answer 8

Insulation

Question 9

Calorimeter Random Errors

Answer 9

• Not all food/substance was combusted (lower energy content than should be)
• incomplete combustion (less energy released)
• inaccurate temp recorded
• MANY REPEATS to minimise

Question 10

Calorimeters Systematic Errors

Answer 10

• poor insulation
• calibrated incorrectly (CF = lower, energy content = lower)
• measurements used to calibrate = measured incorrectly (affects energy calculation)