Chemistry (Module 02) Exercises Solutions

Hi Students,

Welcome to Chemistry Module 02. Once again, thank you for giving us a chance to help you in the revision of O-Level Chemistry. There will more and more topics to be covered in this module. Please commit yourself to complete all those exercises that provided to you at the back of the notes.

The solutions are given here.
Unit 07
Unit 08
Unit 09
Unit 10
Unit 11
Unit 12
Unit 13
Unit 14

Why Some Strong Acids are LESS Corrosive Than Weak Acids?

Hi Students,

Most of the the students are confused confused in the above mentioned questions. They always thought that weak acids must not be corrosive. This is a wrong concept. Let us revise again the topics of Acids and Bases.

Strong Acids
Strong acids completely dissociate in water, forming H+ and an anion.
There are six strong acids:

1. HCl - hydrochloric acid
2. HNO3 - nitric acid
3. H2SO4 - sulfuric acid
4. HBr - hydrobromic acid
5. HI - hydroiodic acid
6. HClO4 - perchloric acid

Weak Acids
A weak acid only partially dissociates in water to give H+ and the anion. Examples of weak acids include hydrofluoric acid, HF, and acetic acid, CH3COOH.

Strong is Different from Corrosive

Corrosiveness is related to the negatively-charged part of the acid. Hydrofluoric acid (HF), for example, is so corrosve it dissolves glass. The fluoride ion attacks the silicon atom in silica glass while the proton is interacting with oxygen. Even though it is highly corrosive, hydrofluoric acid is not considered to be a strong acid because it does not completely dissociate in water.

Acid Rain in Singapore

Acid rain has been affecting the marine life in Singapore since 20 years ago. Please read through the article and understand more about the consequences of the acid rain.