Learn Unit I: Chemical Substances - Nature and Behaviour with Free Lessons & Tips

Some elements exist in molecular form because their atoms prefer to share electrons to achieve a stable electron configuration through covalent bonding. Other elements exist in atomic form because they tend to form metallic bonds or ionic bonds, or because they are noble gases with stable electron configurations.

• Identification of Metal A and Amphoteric Oxide B:

  • Metal A used in the thermite process is iron (Fe).
  • Oxide B is iron(III) oxide (Fe2O3), which is amphoteric in nature.
  • Reactions of oxide B with HCl and NaOH:
    • With HCl: Fe2O3(s) + 6HCl(aq) → 2FeCl3(aq) + 3H2O(l)
    • With NaOH: Fe2O3(s) + 6NaOH(aq) → 2Na3Fe(OH)6

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• Identification of Non-metal A and Its Oxides B and C:

  • Non-metal A is carbon (C).
  • Oxide B is carbon monoxide (CO), which is toxic.
  • Oxide C is carbon dioxide (CO2), which contributes to global warming.

• Rainwater conducts electricity because it contains dissolved ions and gases from the atmosphere, such as carbon dioxide (CO2), oxygen (O2), and nitrogen oxides (NOx), which act as electrolytes and facilitate the flow of electric current. Distilled water, on the other hand, does not conduct electricity because it lacks dissolved ions and gases, making it a poor conductor of electricity.

• Sour substances contain acidic compounds that can react with copper and brass to form toxic compounds such as copper acetate or copper sulfate. These compounds can leach into the food or drink stored in the vessels, posing health risks. Therefore, it is not advisable to keep sour substances in brass and copper vessels.