2016年5月IB化学SL真题下载-Paper3
1. The absorption of infrared (IR) radiation by molecules in the atmosphere affects global temperatures.
(a) Using the graph, state, giving your reasons, whether or not oxygen and ozone are greenhouse gases.
(b) The following data has been compiled for a range of molecules that may be found in the atmosphere.
*Integrated IR intensity is a measure of the extent to which the molecule absorbs infrared radiation passing through the atmosphere.
**GWP: The global warming potential (GWP) is a relative measure of the total contribution of the compound to global warming over the specified time period. It is compared to the same mass of CO2, which has a GWP of 1.
(i) Use the integrated IR intensity data in the table to estimate the value for CF4.
(ii) Explain the increase in molecular dipole moment as one chlorine atom in CCl4 is replaced with fluorine to produce CCl3F.
(iii) Outline the relationship between GWP over 100 years and integrated IR intensity for CCl4, CCl3F, CCl2F2 and CClF3.
(iv) Examine whether there is a general relationship between integrated IR intensity and molecular dipole moment.
(v) CCl2F2 and CClF3 were developed for use as refrigerants but are now being replaced by other chemicals. Comment on their use with reference to values in the table and other environmental concerns.
2. A student wished to determine the concentration of a solution of sodium hydroxide by titrating it against a 0.100 mol dm−3 aqueous solution of hydrochloric acid.4.00 g of sodium hydroxide pellets were used to make 1.00 dm3 aqueous solution. 20.0 cm3 samples of the sodium hydroxide solution were titrated using bromothymol blue as the indicator.
(a) Outline, giving your reasons, how you would carefully prepare the 1.00 dm3 aqueous solution from the 4.00 g sodium hydroxide pellets.
(b) (i) State the colour change of the indicator that the student would see during his titration using section 22 of the data booklet.
(ii) The student added the acid too quickly. Outline, giving your reason, how this could have affected the calculated concentration.
(c) Suggest why, despite preparing the solution and performing the titrations very carefully,widely different results were obtained.
2016年5月IB化学SL真题余下省略！
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