Acids, Bases and Salts | Class 10 Science Notes

2.1 Understanding the Chemical Properties of Acids and Bases

This section explores the chemical properties of acids and bases through various laboratory activities. Acids such as hydrochloric acid (HCl), sulphuric acid (H2SO4), nitric acid (HNO3), and acetic acid (CH3COOH) and bases like sodium hydroxide (NaOH), calcium hydroxide [Ca(OH)2], potassium hydroxide (KOH), magnesium hydroxide [Mg(OH)2], and ammonium hydroxide (NH4OH) are tested with indicators. Indicators like red and blue litmus, phenolphthalein, and methyl orange change color depending on the acidic or basic nature of the solution. Olfactory indicators, substances whose odour changes in acidic or basic media, such as onion, vanilla essence, and clove oil, are also explored. Acids react with metals like zinc to produce hydrogen gas and salts, demonstrating their acidic nature. The reaction is summarized as Acid + Metal → Salt + Hydrogen gas. Bases also react with metals, for example, zinc reacts with sodium hydroxide to form sodium zincate and hydrogen gas. Metal carbonates and hydrogencarbonates react with acids to produce salt, carbon dioxide, and water. The reaction is Metal carbonate/hydrogencarbonate + Acid → Salt + CO2 + Water. Acids and bases neutralize each other to form salt and water, a reaction called neutralization. Metallic oxides react with acids to form salt and water, indicating metallic oxides are basic oxides. Conversely, non-metallic oxides like carbon dioxide react with bases to form salt and water, showing non-metallic oxides are acidic oxides.

📊 Diagram: Figure 2.1 Reaction of zinc granules with dilute sulphuric acid and testing hydrogen gas by burning; Figure 2.2 Passing carbon dioxide gas through calcium hydroxide solution.

🧪 Activity: Activity 2.1: Testing various acids and bases with indicators; Activity 2.2: Using olfactory indicators like onion, vanilla, and clove oil; Activity 2.3: Reaction of zinc with dilute sulphuric acid producing hydrogen gas; Activity 2.4: Reaction of zinc with sodium hydroxide; Activity 2.5: Reaction of metal carbonates and hydrogencarbonates with acids; Activity 2.6: Neutralization reaction between acid and base; Activity 2.7: Reaction of copper oxide with hydrochloric acid.

🔗 Connection: Leads to understanding the common features of acids and bases and their ionic nature in aqueous solutions.