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CBSE Important Questions

CBSE Guess > Papers > Important Questions > Class X > 2014 > Chemistry > Chemistry By Mrs. Kritika Bhola


Chemical Properties of Carbon Compounds

  1. Combustion -- Process of burning of a carbon compound in air to give CO2, water, heat and light.

    • Alkanes burn in air to produce lot of heat due to which they are excellent fuels. Eg. methane , Butane (LPG). They burn in air with blue, non-sooty flame  because the % of carbon in the saturated hydrocarbons is comparatively low which gets oxidized completely by the oxygen present in the air.

    • The stoves have tiny holes for air so that sufficient oxygen is available for complete burning of fuel to produce a smokeless blue flame.

    • Mixture of acetylene(ethyne) and air is not used for welding because burning of ethyne in air produces a sooty flame , which is not hot enough to melt metals for welding.

  2. Substitution reactions --- The reaction in which one or more hydrogen atoms of  hydrocarbons are replaced by some other atoms like  chlorine (chlorination).

    • Saturated hydrocarbons ( alkanes) are unreactive because they contain only carbon-carbon single bonds. They do not react with many substances.
    • They undergo substitution reactions with chlorine in the presence of sunlight.
    • Methane reacts with chlorine in the presence of sunlight to form chloromethane and hydrogen chloride.

      CH4 +  Cl2 → CH3Cl + HCl
      1 H atom of methane is replaced by Cl atom and we get chloromethane .By supplying more chlorine , all H atoms can be replaced by Cl one by one.
      So, we can obtain 3 more compounds ---
      Dichloromethane / methylene dichloride --- CH2Cl2
      Trichloromethane / Chloroform ---- CHCl3

  3. Addition Reactions ---- The unsaturated hydrocarbon combines with another substance to give a single product ( addition of H, Cl or Br)

    • These reactions are given by all unsaturated hydrocarbons containing double or triple bonds ( alkenes and alkynes)
    • Simplest alkene is Ethene which reacts with hydrogen when heated in the presence of nickel catalyst to form ethane  .
    • Unsaturated hydrocarbons add on hydrogen in the presence of catalysts such as Nickel or Palladium(Pd) to form saturated hydrocarbons  which is called HYDROGENATION . This process is used to prepare vegetable Ghee form vegetable oils.

Submitted By Mrs. Kritika Bhola
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