Available Answers

1. 1.

   Explain the term - 'chemical reaction'.

2. 2.

   State whether a physical or a chemical change is involved during - a chemical reaction - giving reasons.

3. 3.

   The equation below represents - a chemical reaction

   2KMnO₄ + 2H₂O + 5SO₂ → K₂SO₄ + 2MnSO₄ + 2H₂SO₄

   1. In the above equation for the chemical reaction - is the equation balanced.
   2. Name the products of the above reaction.
   3. Give a reason why the reactants have formed - new products.
   4. Give an equation for a chemical reaction involving -
      1. Two gases - as the reactants.
      2. A trivalent metal & a dilute acid - as the reactants.
      3. A divalent metal & a non-metal - as the reactants.
4. 4.

   Give a balanced equation for each of the following:

   1. A chemical reaction involving a change in colour - of the reactant to the residual product from -
      1. Blue to black
      2. Orange to green
      3. Light green to black
      4. White to yellow
   2. A chemical reaction resulting in evolution of a gas which -
      1. Turns moist blue litmus faint red, lime water milky and has no effect on acidified KMnO4 soln.
      2. Turns moist red litmus blue & gives dense white fumes with a glass rod dipped in conc. HCI.
      3. Turns moist blue litmus red, lime water milky & acidified KMnO4 soln. from pink to clear colourless.
   3. A chemical reaction resulting in formation of a precipitate
      1. Reddish brown in colour
      2. Pale blue in colour
      3. Dirty green in colour
      4. Gelateneous white in colour
5. 5.

   The different types of chemical reactions maybe represented as -

   1. A + B → AB
   2. AB → A + B
   3. A + BC → AC + B
   4. A⁺ B^- + C⁺ D^- → A⁺ D^- + C⁺ B^-

   1. Match the type of reactions given below with- i], ii], iii], iv]
      1. Double decomposition reaction
      2. Displacement reaction
      3. Direct combination reaction
      4. Decomposition reaction
   2. Define the type of chemical reaction represented by iii].
   3. To which type i.e. i], ii], iii] or iv] - does the reaction given below belong :

   CI₂ + 2KBr → 2KCI + Br₂

   4. In reaction i] - what do A & B represent on the left side.
   5. In reaction iii] - what does 'B' represent on the right side.
   6. State why reaction iv] - is represented as A⁺B^- + C⁺D^- and not as AB + CD.
   7. State why reaction iv] - is represented as precipitation & neutralization. Differentiate between the two.
6. 6.

   Match the different types of chemical changes or energy changes - in a chemical change in Column II with the relevant meaning in Column I.

   Column I	Column II
   1. A chemical reaction in which two or more elements or compounds react to form one new compound as a product.	A: Double decomposition
   2. A chemical reaction in which a chemical compound decomposes or splits up into two or more simpler substances It is generally brought about by heat.	B: Exothermic reaction
   3. A chemical reaction which takes place when an element [or radical] has replaced another element in a compound.	C: Reversible reaction
   4. A reaction in which two reactants are both decomposed to form new substances by exchanging their radicals.	D: Displacement reaction
   5. A chemical reaction which employs a substance to alter the rate of a reaction.	E: Combination or synthesis
   6. A chemical reaction in which the products formed react together to form the original reactants depending on the conditions of the reaction.	F: Decomposition reaction
   7. A reaction in which a substance dissociates into two or more simpler substances on application of heat and is a reversible reaction.	G: Thermal dissociation
   8. A chemical reaction which proceeds with evolution of heat energy.	H: Endothermic reaction
   9. A chemical reaction which proceeds with absorption of heat energy.	I: Catalytic reaction
   10. A chemical reaction which proceeds with absorption of light energy.	J: Photochemical reaction