Question 1

Question 6Compounds such as alcohols and glucose also contain hydrogen but are not categorized as acids. Describe an Activity to prove it.

Accepted Answer

Materials required — Bulb, switch, beaker, nails, battery, connecting wires, glucose, alcohol, hydrochloric acid, sulphuric acidProcedure —Fix two nails on a cork and place the cork in a 100 ml beaker.Connect the nails to the two terminals of a 6 volt battery through a bulb and a switch, as shown in the figure above.Now pour glucose and alcohol solutions one by one and switch on the current.Repeat the activity using hydrochloric acid and sulphuric acid.Observation —The bulb does not glow when glucose and alcohol are used.Bulb glows when hydrochloric acid and sulphuric acid are used.Result — Glowing of the bulb indicates that there is a flow of electric current through the solution. The electric current is carried through the acidic solution by ions.This activity proves that hydrogen containing compounds alcohols and glucose do not ionise to give H+(aq) ions, hence, they are not categorized as acids.

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  Science | Chapter 2: Acids, Bases and SaltsWeb Content

Chapter 2: Acids, Bases and Salts &mdash; Quick Revision Guide

Introduction
      Acids and bases are fundamental chemical substances found everywhere in daily life. This chapter explores their properties, the pH scale, neutralisation reactions, and the preparation of important salts.

Key Points at a Glance
      
        Acids produce H+ (H3O+) ions in water; bases produce OH&minus; ions
        Indicators: Litmus (red/blue), methyl orange, phenolphthalein, turmeric; olfactory indicators change smell
        Acid reactions: with metals (salt + H2), carbonates (salt + H2O + CO2), metal oxides (salt + H2O), bases (neutralisation)
        pH scale: 0&ndash;14; pH < 7 acidic, pH = 7 neutral, pH > 7 basic; measured by universal indicator
        pH importance: stomach (1&ndash;2), blood (7.35&ndash;7.45), tooth decay below pH 5.5, soil pH for agriculture
        Always add acid to water (dilution is exothermic); dry HCl gas does not affect litmus
        Chlor-alkali process: electrolysis of brine gives NaOH + Cl2 + H2
        Important salts: Bleaching powder (CaOCl2), Baking soda (NaHCO3), Washing soda (Na2CO3&middot;10H2O), Plaster of Paris (CaSO4&middot;&frac12;H2O)
        Water of crystallisation: CuSO4&middot;5H2O (blue) loses water on heating &rarr; CuSO4 (white)

Real-World Connections
      Antacids neutralise excess stomach acid; baking soda makes bread fluffy by releasing CO2; washing soda softens hard water; bleaching powder purifies drinking water; Plaster of Paris is used in fracture casts.

Quick Self-Test (5 Questions)
      
        What is the most important concept you learned from this chapter?
        Can you write three key equations/formulae from this chapter from memory?
        Draw a labelled diagram relevant to this chapter without looking at your notes.
        Explain one real-world application of a concept from this chapter.
        What is one common mistake students make in this chapter, and how can you avoid it?

Further Study
      
        NCERT Textbook Chapter 2
        NCERT Exemplar Problems
        Bright Tutorials Detailed Notes: ch02-acids-bases-salts.html
        Bright Tutorials Practice Questions: ch02-acids-bases-salts.html
        Previous Year CBSE Board Papers

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Question 2

Question 7Why does distilled water not conduct electricity, whereas rain water does?

Accepted Answer

Distilled water consists entirely of molecules. Due to the lack of ions, it does not conduct electricity. Rain water on the other hand contains small traces of acids formed due to the dissolutions of atmospheric gases like carbon dioxide, sulphur dioxide, etc. Hence, due to the presence of ions, rain water can conduct electricity.