CBSE Class 10 Chapter 1 Chemical Reactions and Equations In-text Questions Answer

 CBSE Class 10 Chapter 1 Chemical Reactions and Equations In-text Questions Answer

 

Q1	Why should a magnesium ribbon be cleaned before burning in air?
Ans	To ensure that magnesium burns cleanly in the air, it's important to clean the magnesium ribbon. This is because when magnesium is exposed to the oxygen in the air, it creates a stable layer of magnesium oxide (MgO). To prevent any unwanted reactions with oxygen, the ribbon needs to be cleaned to remove this magnesium oxide layer.

Q2	Write the balanced equation for the following chemical reactions. (i) Hydrogen + Chlorine → Hydrogen chloride (ii) Barium chloride + Aluminium sulphate → Barium sulphate + Aluminium chloride (iii) Sodium + Water → Sodium hydroxide + Hydrogen
Ans	(i) Hydrogen + Chlorine → Hydrogen chloride Ans. H2 + Cl2 → 2HCl (ii) Barium chloride + Aluminium sulphate → Barium sulphate + Aluminium chloride Ans. 3BaCl2 + Al2(SO4)3 →3BaSO4 + 2AlCl3 (iii) Sodium + Water → Sodium hydroxide + Hydrogen Ans. 2Na + 2H2O → 2NaOH + H2

 

Q3	Write a balanced chemical equation with state symbols for the following reactions. (i) Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and the solution of sodium chloride.  (ii) Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water.
Ans	(i) Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and the solution of sodium chloride. Ans.  Na2SO4(aq) + BaCl2(aq) → BaSO4(s) + 2NaCl(aq) (ii) Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water. Ans. NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)

   

Q4	A solution of a substance ‘X’ is used for whitewashing. (i) Name the substance ‘X’ and write its formula.  (ii) Write the reaction of the substance ‘X’ named in (i) above with water.
Ans	(i) Name the substance ‘X’ and write its formula. Ans. Quick lime or Calcium Oxide and its formula is CaO. (ii) Write the reaction of the substance ‘X’ named in (i) above with water. Ans.                                   CaO(s)    +     H2O(l)   →    Ca(OH)2(aq)   +   Heat                                         (Quick lime)                           (Slaked lime)

  

Q5	Why is the amount of gas collected in one of the test tubes in Activity 1.7 double of the amount collected in the other? Name this gas.
Ans	In activity 1.7, one of the test tubes collects twice as much gas as the other because during electrolysis, water breaks down to release two molecules of hydrogen and one molecule of oxygen gas. This means that the amount of hydrogen collected will be twice that of oxygen.

 

Q6	Why does the colour of copper sulphate solution change when an iron nail is dipped in it?
Ans	When an iron nail is dipped in a solution of copper sulfate, iron displaces copper from the copper sulfate solution because iron is more reactive than copper. As a result, the color of the copper sulfate solution changes and the reaction can be represented as: Fe + CuSO4 → FeSO4 + Cu

 

Q7	Give an example of a double displacement reaction other than the one given in Activity 1.1
Ans	The reaction between silver nitrate (AgNO3) and sodium chloride (NaCl) is a classic example of a double displacement reaction. In this reaction, the exchange of negative and positive ions occurs, leading to the formation of a white precipitate known as silver chloride. The chemical reaction can be expressed as follows:

 

Q8	Identify the substances that are oxidized and the substances that are reduced in the following reactions: (i) 4Na(s) + O2(g) → 2Na2O(s)  (ii) CuO(s) + H2(g) → Cu(s) + H2O(l)
Ans	(i) 4Na(s) + O2(g) → 2Na2O(s) Ans. Na (ii) CuO(s) + H2(g) → Cu(s) + H2O(l) Ans. Cu