This is a core topic in O Level Chemistry that often confuses students because of the many reactions, properties, and exceptions. Yet, acids, bases, and salts are everywhere in our daily lives—from vinegar and lemon juice to soaps and cleaning products. Mastering this topic is essential not only for exams but also for building a strong chemistry foundation.
What are Acids?
Acids are substances that produce hydrogen ions (H⁺) when dissolved in water. You’ll find them in both household items (like citric acid in fruits) and in the lab (like hydrochloric acid and sulphuric acid).
Properties of Acids (O Level Chemistry pH Focus)
- Sour taste and corrosive in concentrated form.
- pH is less than 7.
- Turn blue litmus paper red.
- Strong acids (e.g., HCl, H₂SO₄) ionize completely, producing many H⁺ ions.
- Weak acids (e.g., CH₃COOH) only partially ionize.
Reactions of Acids
- Acid + metal → salt + hydrogen gas
- Acid + carbonate → salt + carbon dioxide + water
- Acid + base/alkali → salt + water (O Level Chemistry neutralization)
What are Bases and Alkalis?
Bases are substances that react with acids to form salts and water. When bases dissolve in water, they become alkalis, producing hydroxide ions (OH⁻).
Properties of Bases and Alkalis
- pH greater than 7.
- Turn red litmus paper blue.
- Feel slippery but can be corrosive.
Reactions of Alkalis
- Alkali + acid → salt + water
- Alkali + ammonium salt → salt + ammonia gas + water
This is why understanding the properties of acids and bases O Level is crucial for handling exam questions on neutralization.
The World of Salts
Salts are compounds formed when the hydrogen in an acid is replaced by a metal or ammonium ion. For example:
- Hydrochloric acid + sodium hydroxide → sodium chloride + water
Solubility Rules (O Level Chemistry Must-Know)
- Always soluble: sodium, potassium, ammonium salts, all nitrates
- Soluble with exceptions: chlorides, sulphates (e.g., silver chloride and barium sulphate are insoluble)
- Mostly insoluble: carbonates (except sodium, potassium, ammonium)
Salt Preparation Methods (O Level Chemistry Salt Preparation)
- Neutralization (Titration method for soluble salts) - Acid + alkali with indicator, then repeat without indicator to crystallize salt.
- Reaction of Acid and Insoluble Base - Add base until no more reacts, filter excess, and evaporate solution to form crystals.
- Precipitation (for insoluble salts) - Mix two soluble solutions, filter out the precipitate, wash, and dry.
pH Scale & Neutralization
The O Level Chemistry pH scale runs from 0 to 14:
- Acids: 1–6
- Neutral: 7
- Bases/alkalis: 8–14
Neutralization is one of the most important reactions:
- Acid + alkali → salt + water
Applications include:
- Antacids neutralizing excess stomach acid
- Farmers adding lime to neutralize acidic soil
Simplifying Complex Reactions
Students often get lost in the many equations and preparation methods. Using flowcharts can make it easier to visualize:
Acid → reacts with base/alkali → Neutralization → Salt + Water
Acid → reacts with carbonate → Salt + Water + CO₂
Solution A + Solution B → Precipitation → Insoluble Salt
These simple pathways help with revision and quick recall.
Strengthen Your Foundations with O Level Chemistry Tuition
Struggling with O Level Chemistry acids bases salts? You’re not alone. Many students find it hard to memorize solubility rules O Level or to apply the concept of neutralization in problem-solving.
That’s where O Level Chemistry tuition acids lessons can help. Our tutors explain concepts step by step, use real-life examples, and give plenty of practice in salt preparation and pH calculations. With guidance, the most complex reactions become clear and manageable—helping you approach exams with confidence.