Available Answers

1. 1.

   Explain the term 'chemical reaction' with special reference to- 'reactants & 'products'.

2. 2.

   Represent the addition of dilute sulphuric acid to zinc by means of a chemical equation. State the function of the arrow between the reactants  & products.

3. 3.

   A chemical reaction is generally accompanied by certain external indictions or characteristics.

   These include - change of- 

   1. colour
   2. state
   3. smell
   4. evolution of gas
   5. formation of precipitate
   6. evolution or absorption of heat. 

   With reference to change of colour - state the change in colour seen when the following are heated

   1. copper carbonate
   2. zinc carbonate
   3. mercury [II] oxide
   4. lead [IV] oxide
4. 4.

   Give a balanced equation for addition of iron to copper  sulphate solution. State the change in colour seen.

5. 5.

   In certain reactions change of state is observed i.e. solid to liquid, liquid to gas, etc. State the change of state of the reactants - to give the respective products in each case.

   1. C + 2S → CS₂
   2. NH₃ + HCl ⇄ NH₄Cl
   3. 2H₂ + O₂  → 2H₂O
   4. 2H₂O → (electric current) 2H₂ + O₂
6. 6.

   In certain reactions a change of smell is observed. Give two examples from daily life of the same.