化學 2010 年 DSE、CE 選擇題（第 3 頁）

21.

Which of the following substances contain(s) mainly calcium carbonate ?

(1)rock salt

(2)limestone

(3)oyster shell

22.

Which of the following statements concerning potassium and calcium is / are correct ?

(1)The reducing power of potassium is stronger than that of calcium.

(2)The hardness of potassium is higher than that of calcium.

(3)The density of potassium is greater than that of calcium.

23.

The oxide of metal Z reacts with dilute hydrochloric acid to form a colourless solution. Which of the following metals may Z be ?

(1)zinc

(2)copper

(3)silver

24.

Which of the following is / are redox reaction(s) ?

(1)CH₄ + Cl₂ → CH₃Cl + HCl

(2)2 CrO₄²⁻ + 2 H⁺ → Cr₂O₇²⁻ + H₂O

(3)2 KNO₃ → 2 KNO₂ + O₂

25.

Which of the following measures can help improve the air quality in Hong Kong ?

(1)Use natural gas to replace coal in generating electricity.

(2)Use electricity to replace petrol to drive cars.

(3)Use fuel with lower sulphur content to drive ferries.

26.

Which of the following safety measures should be taken when investigating the reaction between sodium and water ?

(1)Use forceps to pick sodium.

(2)Use a small piece of sodium.

(3)Use a small amount of water.

27.

Which of the following environmental problems may be reduced by installing catalytic converters in petrol-driven cars ?

(1)acid rain

(2)greenhouse effect

(3)photochemical smog

28.

For Questions 28–30, decide whether each of the two statements is true or false. If both are true, decide whether the second correctly explains the first.

A.Both are true and the second correctly explains the first.

B.Both are true but the second does not correctly explain the first.

C.The first is false but the second is true.

D.Both are false.

1st statement	2nd statement
Solid citric acid can turn dry blue litmus paper red.	Solid citric acid contains hydrogen ions.

29.

For Questions 28–30, decide whether each of the two statements is true or false. If both are true, decide whether the second correctly explains the first.

A.Both are true and the second correctly explains the first.

B.Both are true but the second does not correctly explain the first.

C.The first is false but the second is true.

D.Both are false.

1st statement	2nd statement
When using a Bunsen burner with the air hole closed, the burner gives a non-luminous flame.	When using a Bunsen burner with the air hole closed, the fuel undergoes incomplete combustion.

30.

For Questions 28–30, decide whether each of the two statements is true or false. If both are true, decide whether the second correctly explains the first.

A.Both are true and the second correctly explains the first.

B.Both are true but the second does not correctly explain the first.

C.The first is false but the second is true.

D.Both are false.

1st statement	2nd statement
Bromine water can react with NaI(aq).	The reducing power of I⁻(aq) ion is stronger than that of Br⁻(aq) ion.