化學 2005 年 DSE、CE 選擇題（第 4 頁）

31.

Which of the following statements concerning 20 cm³ of 1 M CH₃COOH and 10 cm³ of 1 M H₂SO₄ is correct?

32.

Which of the following properties of Group I elements decreases down the group ?

33.

Methane burns completely in oxygen according to the following equation: CH₄ + 2O₂ → CO₂ + 2H₂O What is the mass of oxygen required for the complete combustion of 48 g of methane? (Relative atomic masses: H = 1.0, C = 12.0, O = 16.0)

34.

Which of the following pairs of substances would NOT react together?

35.

Directions: Q.39 to 41 refer to the following information. In an experiment to determine the concentration of sulphuric acid in a brand of toilet cleaner, 25.0 cm³ of the cleaner was first diluted to 250.0 cm³ with distilled water. Upon titration with 0.950 M sodium hydroxide solution using phenolphthalein as indicator, 25.0 cm³ of the diluted cleaner required 27.1 cm³ of the sodium hydroxide solution to reach the end point.

Which of the following types of apparatus should be used to measure 25.0 cm³ of the toilet cleaner?

36.

Directions: Q.39 to 41 refer to the following information. In an experiment to determine the concentration of sulphuric acid in a brand of toilet cleaner, 25.0 cm³ of the cleaner was first diluted to 250.0 cm³ with distilled water. Upon titration with 0.950 M sodium hydroxide solution using phenolphthalein as indicator, 25.0 cm³ of the diluted cleaner required 27.1 cm³ of the sodium hydroxide solution to reach the end point.

What is the colour change at the end point of the titration?

37.

Directions: Q.39 to 41 refer to the following information. In an experiment to determine the concentration of sulphuric acid in a brand of toilet cleaner, 25.0 cm³ of the cleaner was first diluted to 250.0 cm³ with distilled water. Upon titration with 0.950 M sodium hydroxide solution using phenolphthalein as indicator, 25.0 cm³ of the diluted cleaner required 27.1 cm³ of the sodium hydroxide solution to reach the end point.

What is the concentration of sulphuric acid in the undiluted toilet cleaner?

38.

Which of the following statements concerning soaps are correct ?

(1)Soaps are biodegradable.

(2)Soaps have good cleaning power in hard water.

(3)The structure of a soap particle consists of a hydrophilic part and a hydrophobic part.

39.

Consider the reaction represented by the equation below:

C(s) + H₂O(g) ⇌ CO(g) + H₂(g)

Which of the following statements concerning this reaction are correct?

(1)It is a reversible reaction.

(2)The raw materials for the reactants are readily available in nature.

(3)The product mixture formed can be used as a gaseous fuel.

40.

Which of the following statements concerning 1 mole of aluminium is/are correct?

(Avogadro's constant = 6.02 × 10²³;

molar volume of gas at room temperature and pressure = 24 dm³)

(1)It can form 1 mole of Al³⁺ ions.

(2)It can form 3 × 6.02 × 10²³ Al³⁺ ions.

(3)It occupies 24 cm³ at room temperature and pressure.