Alkanes exam questions Flashcards
Sulfur dioxide is produced in the combustion of fossil fuels. The total
emissions of sulfur dioxide in the UK have fallen dramatically since 1970.
Sulfur dioxide is now removed from the flue gases in power stations by
reaction with calcium oxide.
CaO + SO2 → CaSO3
In 1970, the total UK emissions of sulfur dioxide were 6.49 million tonnes
(1 tonne = 1000 kg).
Calculate the mass, in kilograms, of calcium oxide needed to react with this
mass of sulfur dioxide.
Give your answer in standard form.
Moles SO2=6,490,000x10^6/64.1=1.012x10^11
Moles CaO=1.012x10^11 x 56.1/1000=5.68x10^9
Suggest one reason, other than the use of mean bond enthalpies, why a
value for the enthalpy of combustion of a liquid alkane is different from the
value obtained using the expression in part (b)
Idea that
* alkane is not gaseous or
* equation relates to gaseous alkanes or
* it takes energy to convert it into a gas or
* that water / alkane / substances are gaseous in calculations using
bond enthalpies
Isooctane (2,2,4-trimethylpentane) is an important component of petrol
used in cars.
When isooctane is burned, the enthalpy change is −47.8 kJ g−1
Isooctane is a liquid at room temperature with a density of 0.692 g cm−3
Calculate the heat energy released, in kJ, when 1.00 dm3 of isooctane
burns in excess oxygen.
Give your answer to the appropriate number of significant figures.
M1 mass of isooctane = 692
3.31 × 104 or 33100 (kJ) (3sf only)
