Senior Secondary (HKDSE) · Chemistry

Important compounds: aspirin, detergents, nylon, polyesters: Practice Questions

5 multiple-choice questions marked as you go, and 5 written questions with worked solutions. All on Important compounds: aspirin, detergents, nylon, polyesters.

10 questions29 marksFree, no account

Question 1

1 mark

Which statement correctly describes the nature of the hydrophilic part of a soapless detergent molecule?

Question 2

1 mark

Nylon 6,6 is a polyamide formed by the condensation polymerization of hexamethylenediamine and adipic acid. During this reaction, what type of small molecule is eliminated for each bond formed between monomers?

Question 3

1 mark

Both soaps and soapless detergents are used for cleaning, but soapless detergents are generally more effective in hard water. This difference is primarily due to the chemical nature of their hydrophilic head groups. Which statement best explains why soapless detergents perform better in hard water?

Question 4

1 mark

Which of the following best describes the primary role of the hydrophobic tail of a detergent molecule during the cleansing process?

Question 5

1 mark

Polyesters are known for their varied applications, including fabrics and plastic bottles. Which characteristic property of polyesters contributes most to their use in durable and crease-resistant textiles?

Question 6

2 marks

Briefly describe how the hydrophobic tail of a soapless detergent molecule interacts with oil during the cleansing process.

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Question 7

3 marks

Nylon and polyesters are common synthetic fibers used in the textile industry. State the specific type of polymerisation reaction involved in their formation and name ONE small molecule that is typically eliminated during this process.

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Question 8

5 marks

Nylon, a polyamide, is known for its high tensile strength. Explain how the molecular structure of nylon contributes to this property, specifically mentioning the type of intermolecular forces involved.

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Question 9

6 marks

Detergents are indispensable in modern cleaning. They can be broadly classified into soaps and soapless detergents, each with distinct structural features and cleansing actions.

(a) State the structural formula of sodium stearate, a typical soap. Identify its hydrophobic and hydrophilic parts.
(b) State the structural formula of sodium dodecylbenzenesulfonate, a common anionic soapless detergent. Identify its hydrophobic and hydrophilic parts.
(c) Explain why soapless detergents are generally more effective in hard water than soaps, referring to the chemical species involved.

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Question 10

8 marks

Aspirin (acetylsalicylic acid) is a widely used drug known for its analgesic, anti-inflammatory, and antipyretic properties. Its effectiveness is closely related to its chemical structure and reactivity.

(a) Draw the full structural formula of aspirin. Identify and label its two characteristic functional groups.
(b) Aspirin is insoluble in pure water but becomes soluble when added to an aqueous sodium carbonate solution.
(i) Write a chemical equation for the reaction that occurs when aspirin is added to aqueous sodium carbonate solution.
(ii) Explain why aspirin becomes soluble in this solution.
(c) Aspirin tablets stored for a long time, especially in humid conditions, may develop a distinct vinegar-like smell.
(i) Name the organic compound primarily responsible for this smell.
(ii) Explain the chemical process occurring and suggest a suitable storage condition to minimize this decomposition.

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