2016年11月IB化学SL真题下载-Paper2
1. Ethane-1,2-diol, HOCH2CH2OH, has a wide variety of uses including the removal of ice from aircraft and heat transfer in a solar cell.
(a) Ethane-1,2-diol can be formed according to the following reaction.
2CO (g) + 3H2 (g) ⇔HOCH2CH2OH (g)
(i) Deduce the equilibrium constant expression, Kc , for this reaction.
(ii) State how increasing the pressure of the reaction mixture at constant temperature will affect the position of equilibrium and the value of Kc .
Position of equilibrium:
Kc:
(iii) Calculate the enthalpy change, ΔHØ, in kJ, for this reaction using section 11 of the data booklet. The bond enthalpy of the carbon–oxygen bond in CO (g) is 1077 kJ mol-1.
(iv) The enthalpy change, ΔHØ, for the following similar reaction is –233.8 kJ.
2CO (g) + 3H2 (g) ⇔ HOCH2CH2OH (l)
Deduce why this value differs from your answer to (a)(iii).
(b) Determine the average oxidation state of carbon in ethene and in ethane-1,2-diol.
Ethene:
Ethane-1,2-diol:
(c) Explain why the boiling point of ethane-1,2-diol is significantly greater than that of ethene.
(d) Ethane-1,2-diol can be oxidized first to ethanedioic acid, (COOH)2, and then to carbon dioxide and water. Suggest the reagents to oxidize ethane-1,2-diol.
2. The concentration of a solution of a weak acid, such as ethanedioic acid, can be determined by titration with a standard solution of sodium hydroxide, NaOH (aq).
(a) Distinguish between a weak acid and a strong acid.
Weak acid:
Strong acid:
(b) Suggest why it is more convenient to express acidity using the pH scale instead of using the concentration of hydrogen ions.
(c) 5.00 g of an impure sample of hydrated ethanedioic acid, (COOH)2•2H2O, was dissolved in water to make 1.00 dm3 of solution. 25.0 cm3 samples of this solution were titrated against a 0.100 mol dm-3 solution of sodium hydroxide using a suitable indicator.
(COOH)2 (aq) + 2NaOH (aq) → (COONa)2 (aq) + 2H2O (l)
The mean value of the titre was 14.0 cm3.
(i) Calculate the amount, in mol, of NaOH in 14.0 cm3 of 0.100 mol dm-3 solution.
(ii) Calculate the amount, in mol, of ethanedioic acid in each 25.0 cm3 sample.
(iii) Determine the percentage purity of the hydrated ethanedioic acid sample.
(d) The Lewis (electron dot) structure of the ethanedioate ion is shown below.
Outline why all the C–O bond lengths in the ethanedioate ion are the same length and suggest a value for them. Use section 10 of the data booklet.
2016年11月IB化学SL真题余下省略！
你可能还关注