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

4. Two important observations of the reaction are:
   • The mixture produces heat and generates steam, indicating an exothermic reaction.
   • The quicklime dissolves in water to form calcium hydroxide (slaked lime), accompanied by the release of heat and the formation of a milky white suspension.

The type of reaction taking place is a chemical reaction, specifically an exothermic reaction, in which quicklime (calcium oxide) reacts with water to form calcium hydroxide (slaked lime) and release heat.

Double bond or double covalent bond: A double bond, also known as a double covalent bond, is a type of chemical bond formed when two atoms share two pairs of electrons. This sharing of electrons results in the formation of a strong bond between the atoms. Examples of molecules containing double bonds include ethene (C2H4) and oxygen (O2).

Triple bond or triple covalent bond: A triple bond, also known as a triple covalent bond, is a type of chemical bond formed when two atoms share three pairs of electrons. This sharing of electrons results in the formation of a very strong bond between the atoms. Examples of molecules containing triple bonds include nitrogen gas (N2) and acetylene (C2H2).

• Electron Dot Structure of Compound Formed between Metal 'X' and Non-metal 'Y':

  • Metal 'X' loses two electrons, represented as X2+.
  • Non-metal 'Y' gains one electron, represented as Y-.
  • The compound formed between them is ionic, as it involves the transfer of electrons from the metal to the non-metal.
  • It has a high melting point due to strong electrostatic forces of attraction between oppositely charged ions.
  • It will conduct electricity in the molten state or in aqueous solution, as the ions are free to move and carry electric charge.
  • It may or may not be soluble in water, depending on the specific properties of the compound formed.

• Identification and Properties of Metals Mn, Zn, Fe, and Cu:

  • (a) Zn will not displace H2 from dil. HCl.
  • (b) Fe will react only with steam to give H2(g).
  • (c) Cu will give H2 with 5% HNO3.
  • Chemical reactions:
    • Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)
    • Fe(s) + 3H2O(g) → FeO(s) + 3H2(g)
    • Cu(s) + 2HNO3(aq) → Cu(NO3)2(aq) + H2(g)

• Neutralization reaction is a chemical reaction in which an acid reacts with a base to form a salt and water. Two examples of neutralization reactions are:

  • Hydrochloric acid (HCl) + Sodium hydroxide (NaOH) → Sodium chloride (NaCl) + Water (H2O)
  • Sulfuric acid (H2SO4) + Calcium hydroxide (Ca(OH)2) → Calcium sulfate (CaSO4) + Water (H2O)

• Two uses of baking soda are:

  • Baking soda (sodium bicarbonate, NaHCO3) is used as a leavening agent in baking to help dough rise.
  • It is used as an antacid to relieve heartburn, indigestion, and upset stomach by neutralizing excess stomach acid.

  Two uses of washing soda (sodium carbonate, Na2CO3) are:

  • Washing soda is used as a cleaning agent and laundry detergent booster due to its alkaline properties, which help to remove stains and grease.
  • It is used in water treatment processes to soften hard water by precipitating calcium and magnesium ions.