Acids, Bases and Salts

Properties, indicators and uses of acids, bases and salts.

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Acids, Bases and Salts

Overview

Acids, bases and salts form a foundational chapter in upper-primary science, bridging everyday experiences (lemon sourness, soap slipperiness) with core chemical concepts. For WB TET Paper II, this topic tests your understanding of characteristic properties, behaviour with indicators, neutralisation reactions and practical applications. Questions typically ask you to identify substances as acidic or basic, predict indicator colour changes, write simple chemical equations for neutralisation, and recall common uses of acids, bases and salts.

Mastery here requires memorising indicator colour charts, understanding the pH scale conceptually, and knowing real-world examples. The topic also connects to environmental science (acid rain, soil pH) and health (antacids, oral hygiene), making it a favourite for application-based questions.

Key Concepts

**Acids** are substances that release hydrogen ions (H⁺) when dissolved in water. They taste sour, turn blue litmus red and react with metals to produce hydrogen gas.

**Bases** are substances that release hydroxide ions (OH⁻) in water. They taste bitter, feel soapy/slippery and turn red litmus blue.

**Alkalis** are bases that dissolve in water. All alkalis are bases, but not all bases are alkalis (e.g., copper hydroxide is a base but not an alkali).

**Indicators** are substances that show different colours in acidic and basic solutions. Common indicators include litmus, phenolphthalein, methyl orange and turmeric.

**Neutralisation** is the reaction between an acid and a base to form salt and water: Acid + Base → Salt + Water.

**pH Scale** measures the strength of acidity or basicity on a scale of 0–14. pH 7 is neutral; below 7 is acidic; above 7 is basic.

**Salts** are ionic compounds formed by the reaction of acids and bases. They may be acidic, basic or neutral depending on the parent acid and base.

**Strong vs Weak Acids/Bases**: Strong acids (HCl, H₂SO₄) and strong bases (NaOH, KOH) ionise completely; weak acids (acetic acid) and weak bases (NH₄OH) ionise partially.

Formulas / Key Facts

**Chemical Formulas of Common Acids:**

Hydrochloric acid: HCl
Sulphuric acid: H₂SO₄
Nitric acid: HNO₃
Acetic acid (vinegar): CH₃COOH
Carbonic acid: H₂CO₃

**Chemical Formulas of Common Bases:**

Sodium hydroxide (caustic soda): NaOH

Practice this topic

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Q1 · Acids, Bases and Salts · EASY
A student tests a household substance with red litmus paper and observes that it turns blue. Which of the following is most likely the substance being tested?
Q2 · Acids, Bases and Salts · MEDIUM
During a science experiment, a teacher demonstrates the reaction between dilute hydrochloric acid and sodium hydroxide solution. At the end of the reaction, the solution becomes neutral. Which of the following statements correctly describes this process?
Q3 · Acids, Bases and Salts · MEDIUM
A farmer finds that his soil has become too acidic for proper crop growth. He adds a white powder to the soil to neutralise the excess acidity. The powder he most likely used is:
Q4 · Acids, Bases and Salts · HARD
A student prepared a dilute solution of an acid and divided it into three test tubes. She then added: - Zinc metal to tube 1 - Magnesium ribbon to tube 2 - Copper turnings to tube 3 She observed that gas bubbles were evolved in tubes 1 and 2, but not in tube 3. Which of the following explains this observation correctly?
Q5 · Acids, Bases and Salts · MEDIUM
What is the pH value of a neutral solution at 25°C?

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Notes generated on 27 Jun 2026

Acids, Bases and Salts

Acids, Bases and Salts

Overview

Key Concepts

Formulas / Key Facts

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