2019年5月IB化学SL真题下载-Paper2
1.Xylene is a derivative of benzene. One isomer is 1,4-dimethylbenzene.
(a)State the number of 1H NMR signals for this isomer of xylene and the ratio in which they appear.
Number of signals:
Ratio:
(b)Draw the structure of one other isomer of xylene which retains the benzene ring.
(c)Bromine reacts with alkanes.
(i)Identify the initiation step of the reaction and its conditions.
(ii)1,4-dimethylbenzene reacts as a substituted alkane. Draw the structures of the two products of the overall reaction when one molecule of bromine reacts with one molecule of 1,4-dimethylbenzene.
2.Benzoic acid, C6H5COOH, is another derivative of benzene.
(a)Draw the structure of the conjugate base of benzoic acid showing all the atoms and all the bonds. [1]
(b)(i) The pH of an aqueous solution of benzoic acid at 298 K is 2.95. Determine the concentration of hydroxide ions in the solution, using section 2 of the data booklet.
(ii)Formulate the equation for the complete combustion of benzoic acid in oxygen using only integer coefficients.
(c)Suggest how benzoic acid, Mr = 122.13, forms an apparent dimer, Mr = 244.26, when dissolved in a non-polar solvent such as hexane.
3.This question is about compounds of sodium.
(a)(i) Describe the structure and bonding in solid sodium oxide.
(ii)Write equations for the separate reactions of solid sodium oxide and solid phosphorus(V) oxide with excess water and differentiate between the solutions formed.
Sodium oxide, Na2O:
Phosphorus(V) oxide, P4O10:
Differentiation:
(b)Sodium peroxide, Na2O2, is formed by the reaction of sodium oxide with oxygen.
2Na2O (s) + O2 (g) → 2Na2O2 (s)
Calculate the percentage yield of sodium peroxide if 5.00 g of sodium oxide produces 5.50 g of sodium peroxide.
(c)Sodium peroxide is used in diving apparatus to produce oxygen from carbon dioxide.
2Na2O2 (s) + 2CO2 (g) → 2Na2CO3 (s) + O2 (g)
(i)Determine the enthalpy change, ΔH, in kJ, for this reaction using data from the table and section 12 of the data booklet.
(ii)Outline why bond enthalpy values are not valid in calculations such as that in (c)(i).
(d)The reaction of sodium peroxide with excess water produces hydrogen peroxide and one other sodium compound. Suggest the formula of this compound.
(e)State the oxidation number of carbon in sodium carbonate, Na2CO3.
2019年5月IB化学SL真题余下省略！
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