化學 2001 年 DSE、CE 選擇題（第 3 頁）

21.

Consider the half equation: IO₃⁻(aq) + xH₂O(l) + ye⁻ → I⁻(aq) + zOH⁻(aq) Which of the following combinations is correct ?

x	y	z
1	2	2
2	4	4
3	6	6
4	8	8

22.

The reaction involved in the preparation of ethanoic acid from ethanol is

23.

What is the percentage by mass of chromium in potassium dichromate ? (Relative atomic masses: O = 16.0, K = 39.1, Cr = 52.0)

24.

Suppose that the Avogadro number is L. How many atoms does 600 cm³ of oxygen at room temperature and pressure contain? (Molar volume of gas at room temperature and pressure = 24 dm³)

25.

The oxidation number of lead in [Pb(OH)₄]²⁻ is

26.

Which iron nail in the test tubes shown below would rust most slowly ?

27.

Which of the following measures can reduce the emission of sulphur dioxide from a factory using diesel fuel?

(1)the installation of catalytic converters

(2)the installation of scrubbers

(3)the installation of electrostatic precipitators

28.

The formulae of three straight-chain hydrocarbons are listed below:

(1)C₂H₆

(2)C₃H₆

(3)C₄H₈

Which of these hydrocarbons is/are unsaturated?

29.

Consider the information below about the reaction of hydrogen with chlorine:

H₂(g) + Cl₂(g) → 2HCl(g) ΔH < 0

Which of the following statements can be deduced from the above information?

(1)Heat is liberated when hydrogen chloride is formed.

(2)Hydrogen and chlorine react at room temperature.

(3)When measured at room temperature and pressure, the total gas volume before the reaction equals that after the reaction.

30.

In a titration experiment, 25.0 cm³ of diluted vinegar is titrated against a standard solution of sodium hydroxide with phenolphthalein as indicator. Which of the following statements concerning this experiment is/are correct?

(1)The colour of phenolphthalein changes from colourless to pink at the end point.

(2)The colour of phenolphthalein changes from pink to colourless at the end point.

(3)A measuring cylinder is used to measure the volume of the diluted vinegar.