The questions below are all on calorimetry. Each page has only one question on it, and the mark scheme for each question is on the page that immediately follows. A printable copy of the questions can be found here.
Question 1
In Europe, some of the glucose from crops is fermented to produce ethanol.
Use of a carbon-neutral fuel leads to no net emissions of carbon dioxide to the atmosphere.
(a) The ethanol produced by fermentation of glucose may be regarded as a carbon-neutral fuel. Justify this statement. Include the relevant chemical equations in your answer.
(4)
Coffee beans from South America are exported to Europe in an outer layer called silverskin.
The waste silverskin can be fermented to produce a solution containing propanone, ethanol and butan-1-ol.
(b) Suggest why ethanol produced in Europe using silverskin from South America is less likely to be carbon-neutral than ethanol produced from crops grown in Europe.
(1)
(c) Table 1 shows the enthalpies of combustion of the three fuels from the fermentation of silverskin.
One way to measure a fuel’s environmental impact is to measure the amount of energy released per mole of CO2 produced.
Complete Table 1.
Use your answers to deduce the fuel with the lowest environmental impact by this measure.
(2)
(d) A student investigated the combustion of propanone (C3H6O) using calorimetry.
A copper calorimeter containing water was heated by the complete combustion of some propanone. The student did not record the final temperature of the water.
Table 2 shows the student’s results.
Use the results in Table 2 to calculate a value for final temperature of the water in the experiment.
Assume that no heat was lost in the experiment and that the heat capacity of the calorimeter is negligible.
For propanone, enthalpy of combustion = –1786 kJ mol−1
For water, specific heat capacity = 4.18 J g−1 K−1
(4)