化學 2002 年 DSE、CE 選擇題（第 3 頁）

21.

Which of the following objects is least likely to contain titanium ?

22.

Which of the following substances does not conduct electricity in its solid state but does conduct electricity in its liquid state ?

23.

Starch, a natural polymer, is a carbohydrate. When concentrated sulphuric acid is added dropwise to some starch, a black substance is formed. The reaction involved is

24.

A black powder is suspected to be carbon or a mixture of carbon and copper(II) oxide. Which of the following methods can be used to identify the black powder?

(1)adding dilute sulphuric acid to the powder

(2)adding sodium hydroxide solution to the powder

(3)heating the powder strongly

25.

Which of the following reactions is/are endothermic?

(1)the fermentation of glucose

(2)the cracking of naphtha

(3)the reaction of lime with dilute hydrochloric acid

26.

Upon complete combustion, gaseous hydrocarbon X gives an equal number of moles of carbon dioxide and water. Which of the following hydrocarbons may X be?

(1)ethane

(2)ethene

(3)propene

27.

Which of the following statements concerning fluorine is/are correct ?

(1)It exists as monatomic molecules.

(2)It reacts with hydrogen to form a covalent compound.

(3)It reacts with calcium to form a compound with formula CaF₂.

28.

Which of the following set-ups can be used to dry moist sulphur dioxide gas?

29.

Which of the following statements concerning Group VII elements and their ions are correct ?

(1)Chlorine has the highest oxidizing power among chlorine, bromine and iodine.

(2)Iodide ions have the highest reducing power among chloride, bromide and iodide ions.

(3)Bromine is a volatile liquid at room temperature and pressure.

30.

When sulphur dioxide is bubbled into water, a colourless solution is formed. Which of the following statements concerning the solution are correct ?

(1)The solution conducts electricity better than water.

(2)The solution can change iron(III) sulphate solution from yellow to green.

(3)The solution can change potassium bromide solution from colourless to brown.