RBSE Class 10 Science: Chemical Reactions and Equations Important Questions with Answers

The chapter Chemical Reactions and Equations is the most important in RBSE Class 10 Science. We have prepared 100 most important questions for class 10 science chemical reactions and equations.

 

These important questions will be very useful and helpful for you. You should prepare notes yourself and practice them well.

 

Important Questions for Class 10 Science Chemical Reactions and Equations

 

 

1. Define the following terms with a suitable example –

i.              Combination reaction

ii.          Decomposition reaction

iii.       Displacement reaction

iv.        Exothermic reaction

v.           Endothermic reaction

vi.        Oxidation

vii.    Reduction

viii. Precipitation reaction

ix.        Double displacement

x.           Redox reaction

 

Answer

i.    Combination reaction: - The chemical reaction in which two or more reactants (substances) react to produce on single product is called combination reaction.

Example - 2Mg +O₂ →2MgO

ii.          Decomposition reaction: - The chemical reaction in which one complex substance break down into two or more simpler substances, is called decomposition reaction.

Example – CaCO₃ → CaO + CO₂

iii.  Displacement reaction: - The chemical reaction in which one more reactive element displaces or removes less reactive element from its compound, is called displacement reaction.

 Example – Fe + CuSO₄ →FeSO₄   + Cu

iv.  Exothermic reaction: - The chemical reaction in which heat is released during the formation of products, is called exothermic reaction.

 Example - CH₄  + 2O₂  → CO₂  + 2H₂O +heat

 

 v.   Endothermic reaction: - The chemical reaction in which heat is absorbed from surroundings during the formation of products, is called endothermic reaction.

Example – N₂  + O₂  + heat → 2NO

vi.        Oxidation reaction: - The chemical reaction in which a substance gains oxygen or loss hydrogen is called oxidation reaction.

Example -  2Mg  + O₂  → 2MgO

vii.  Reduction reaction: - The chemical reaction in which a substance gains hydrogen or loss oxygen is called reduction reaction.

Example – 2HgO  →2Hg  + O₂

viii. Precipitation reaction: - The chemical reaction in which two aqueous solutions react to form an insoluble substance (precipitate) is called precipitation reaction.

Example - AgNO ₃ +  NaCl     → AgCl↓   +  NaNO₃

ix.  Double displacement reaction: - The chemical reaction in which two compounds exchange their ions and form new two compounds, is called double displacement reaction.

  Example - AgNO ₃ + NaCl     → AgCl   + NaNO₃

x.   Redox reaction: - The chemical reaction in which oxidation and reduction take place simultaneously is called redox reaction.

Example – Zn  + CuSO₄ →ZnSO₄   + Cu

2.  Identify the following reactions and give their name –-

i.      N₂ + H₂ →   NH₃

ii.  H₂O →    H₂     +     O₂

iii. CaCO₃    →     CaO    +    CO₂

iv.   AgNO ₃ + NaCl     → AgCl   + NaNO₃

Answer   - The given reaction is -

i). Combination reaction - Two elements nitrogen and hydrogen combine to form a new single substance    ammonia.

ii). Decomposition reaction – A single compound water breaks down into two simpler substance hydrogen and oxygen.

iii). Decomposition reaction – A single compound calcium carbonate breaks down into two simpler substance calcium oxide and carbon dioxide.

iv). Double displacement reaction – Ion exchange between silver nitrate and sodium chloride.

3. What happens when –(Give the chemical equation for the following reactions)

i.        Calcium carbonate (CaCO₃) is heated.

ii.      Copper is burnt in air.

iii.   Magnesium wire is burnt.

iv.    Natural gas burns.

v.       Quick lime reacts with water.

vi.    Iron nails are put in the solution of copper sulphate.

vii.  Lead nitrate is heated

viii. Silver chloride is kept in sunlight

ix.       Silver bromide is kept in sunlight

x.          Ferrous sulphate is heated

xi.        Carbon dioxide is passed through lime water

Answer

i)     Calcium carbonate decomposes into calcium oxide and carbon dioxide

     CaCO₃    →     CaO    +    CO₂

ii)    Copper reacts with oxygen to form copper (II) oxide which is black in colour.

       2 Cu   + O₂  →2CuO

iii)     Burns with white flame and give white powder of magnesium oxide.

        2Mg +O₂ →2MgO

iv)       Give carbon dioxide, water and heat.

       CH₄  + 2O₂  → CO₂  + 2H₂O +heat

v)         Quick lime give slaked lime (Ca(OH)₂

                CaO + H₂O   →Ca(OH)₂

      vi)            

          vi)Iron displaces copper form its salt solution and a brown layer is deposited on nails and pale green solution is formed

             Fe + CuSO₄ →FeSO₄   + Cu

          vii)     Lead nitrate breaks down into lead oxide, brown nitrogen dioxide and oxygen

             2Pb (NO₃)₂   → 2PbO + 4NO₂   + O₂

                     viii)    Silver chloride decomposes into silver metal and chlorine gas.

              2AgCl → 2Ag + Cl₂

   

         ix)       Silver bromide decomposes into silver metal and bromine gas.

   2AgBr → 2Ag + Br₂

x)      Ferrous sulphate decomposes into ferric oxide, sulphur trioxide and sulphur dioxide.

   2FeSO₄   →  Fe₂O₃   + SO₃    + SO₂

xi)      A milky white precipitate of calcium carbonate appears.

    Ca(OH)₂   +CO₂   → CaCO₃    + H₂O

4. Name any two elements which are more reactive than copper.

Answer

 Zinc and iron are more reactive than copper. They both displace copper from its solution.

5. Write the chemical formula of marble.

Answer

CaCO₃

 

6. Give the equation for the reaction used in respiration?

Answer

  C₆H₁₂O₆   +   6O₂  →  6CO₂   +   6H₂O   + energy

7. Identify the substance that are oxidized and substances that are reduced in the following reactions-

i.        4Na      +    O₂  →    2N₂O

ii.       CuO     +    H₂     → Cu     +    H₂O

Answer

i). Substance oxidized – Na

    Substance reduced – O₂

ii). Substance oxidized – H₂

    Substance reduced -  CuO

 

8. Write the chemical equations for the following statements--

i.     Hydrogen gas combines with nitrogen to form ammonia.

ii.  Barium chloride reacts with aluminium sulphate to give aluminium chloride and barium sulphate.

Answer

i). 3H₂   + N₂  → 2NH₃

ii). BaCl₂  + Al₂(SO₄)₃  →AlCl₃  + BaSO₄

 

 

9. Define the following-

i.     Word equation

ii.    Skeletal equation

iii.  Corrosion

iv.   Rancidity

Answer

i). Word equation: - Chemical equation in which names of reactants and products are written is called word equation.

 Example – Hydrogen + Oxygen → Water

ii). Skeletal equation: - The unbalanced chemical equation in which formula of reactants and products are written, is skeletal equation.

 Example        H₂    + O₂   → H₂O

iii). Corrosion:- The process of eating away of the metal by the action of atmospheric reagents changing the metal into its compounds is called corrosion.

Example – Rusting of iron

iv). Rancidity: - When food items are kept unprotected for some time, they give some unpleasant smell and taste or become rancid. This process is called rancidity.

 

10.  Why does the colour of copper sulphate solution change when an iron nail is dipped in it?

Answer

Iron is more reactive than copper. So, iron displaces copper form copper sulphate solution and forms ferrous sulphate solution which is of light green colour.

 

 Fe + CuSO₄ →FeSO₄   + Cu