Chemical Reactions & Equations - 10th CBSE

Very short Answer Type Questions:
1. State whether the following statement is true (or) false
    A chemical equation can be balanced easily by altering the formula of a reactant or product.
Ans : False

2. What is wrong with the following chemical equation?
                   Mg + O ----------> MgO
                Correct and balance it.
Ans : Oxygen should be in molecular form, O₂; 2Mg + O₂ -----------> 2MgO

3. Translate the following statements into chemical equations and then balance the equations:
   (a) Hydrogen sulphide gas burns in air to give water and sulphur dioxide.
   (b) Phosphorus burns in oxygen to give phosphorus pentoxide.
   (c) Aluminium metal replaces iron from ferric oxide, Fe₂O₃, giving aluminium oxide and iron.
   (d) Carbon disulphide burns in air to give carbon dioxide and sulphur dioxide.
   (e) Barium chloride reacts with zinc sulphate to give zinc chloride and barium sulphate.
Ans :
   (a) 2H₂S + 3O₂ --------> 2H₂O + SO₂
   (b) P₄ + 5O₂ ------------> 2P₂O₅
   (c) 2Al + Fe₂O₃ ----------> Al₂O₃ + 2Fe
   (d) CS₂ + 3O₂ --------> CO₂ + 2SO₂
   (e) Bacl₂ + ZnSO₄  ---------> ZnCl₂ + BaSO₄

Practical  Based Questions

1. You want to study a decomposition reaction by taking ferrous sulphate crystals in a boiling tube. List 2 precautions you would follow while doing the experiment.

Ans: 1) Take a dry boiling tube.

         2) Keep mouth of test - tube away from yourself.

2. On keeping iron nails in blue coloured copper sulphate  solution, it is observed that the colour of the solution turns light green after some time. Give reason for this colour change. Name the type of this reaction.

Ans: 1) Copper is displaced by iron.

        2) It is displacement reaction.

3. What happens when barium chloride solution and sodium sulphate  solution are mixed togrther? Write the chemical equation.

Ans: An insoluble salt is formed, which is barium sulphate and white in colour.

      Bacl₂(aq)  + Na₂SO₄(aq)   →  BaSO₄(s) + 2NaCl(aq) 

                                                    (white ppt)

4. Solution of ferrous sulphate, zinc sulphate, copper sulphate and aluminium sulphate were separately taken in four test - tubes and some iron nails were placed in each of the solutions. What will you observe after few seconds?

Ans: Iron will react only with CuSO₄ solution as Fe is more reactive than Cu.

5. A student added aluminium pieces in ferrous sulphate solution  taken in test - tube. Write down the colour change she observed in the solution?

Ans: Solution becomes pale green to colourless.

6. Ashok took two test - tubes A and B containing pale green and blue solutions respectively. Write down the name of the respective solutions taken in test tube A and B?

Ans: Solution taken in A is FeSO₄ and B is CuSO₄.