Interpreting graphical and tabulated data
Industrial chemical processes provide some excellent opportunities for students to develop and practice their skills in interpreting graphical and tabular data.
Some students find it difficult to interpret graphs and may need help in understanding what they mean. The following example is based on the Contact process, for which the key step is the conversion of SO2 to SO3.
2SO2(g) + O2(g) 2SO3(g)
[INSERT EII_EU_08_ima]
What happens to Kp with increasing temperature?
K p increases with increasing temperature.
)})
What is the approximate conversion of SO2 to SO3 at 450 ºC?
Approximately 97%.
Why is the process operated at atmospheric pressure even though the increase in pressure would increase the percentage yield of SO3?
The percentage conversion of SO2 to SO3 is sufficiently high at atmospheric pressure so there is no need to incur the additional costs of operating at a higher pressure.
Students should also be given practice in making sense of tabulated data so that they develop the skill of identifying trends in numerical data. The example below uses data from the manufacture of methanol using synthesis gas:
CO(g) + 2H2(g) CH3OH(g)
The percentage of methanol produced at different temperatures is shown in the table below (LabMouse chemistry).
| Temperature/ºC | 200 | 225 | 250 | 275 | 300 | 325 | 350 |
| % methanol | 16.0 | 14.0 | 11.6 | 8.0 | 5.2 | 3.0 | 1.6 |
What does the data suggest about the reaction between CO and H2?
The data indicates that the reaction is exothermic. In fact ΔH = –91 kJ mol–1.