NCERT Exemplar - Acids, Bases and Salts Notes | EduRev

Science Class 10

Class 10 : NCERT Exemplar - Acids, Bases and Salts Notes | EduRev

The document NCERT Exemplar - Acids, Bases and Salts Notes | EduRev is a part of the Class 10 Course Science Class 10.
All you need of Class 10 at this link: Class 10

Short Answer Type Questions

Q.1. Match the important chemicals given in Column (A) with the chemical formula given in Column (B).
NCERT Exemplar - Acids, Bases and Salts Notes | EduRev
Ans.
NCERT Exemplar - Acids, Bases and Salts Notes | EduRev

Q.2. What will be the action of the following substances on litmus paper?
Dry HCl gas, Moistened NHgas, Lemon juice, Carbonated soft drink, Curd, Soap solution.
Ans.
 

  • Dry HCl gas will not have any effect on litmus paper.
  • Moistened NH3 gas will turn red litmus blue.
    NCERT Exemplar - Acids, Bases and Salts Notes | EduRev
    Moist NH3 turned red litmus blue
  • Curd, lemon juice, carbonated soft drink will turn blue litmus red.
  • Soap solution will turn red litmus blue.

Q.3. Name the acid present in ant sting and give its chemical formula. Also, give the common method to get relief from the discomfort caused by the ant sting.
Ans.
Ant sting contains methanoic acid (formic acid). Its chemical formula is HCOOH. The common method to get relief is to apply a paste of NaHCO3 (baking soda) on it or any basic substance to neutralize it.

Q.4. What happens when nitric acid is added to eggshell?
Ans. Egg-shell is made up of calcium carbonate, which will react with HNO3 to form CO2 (g) and H2O (l) along with calcium nitrate.
Example: CaCO3 + 2HNO3 → Ca(NO3)2 + CO2 + H2O

Q.5. A student prepared solutions of (i) an acid and (ii) a base in two separate beakers. She forgot to label the solutions, and litmus paper is not available in the laboratory. Since both the solutions are colourless, how will she distinguish between the two?
Ans.

  • Add phenolphthalein to a portion of each solution in a separate test tube. 
  • If it turns pink, the beaker contains a base, whereas if it remains colourless, it is an acid. 
  • If phenolphthalein is not available, pH paper can be used. 
  • Acid will turn pH paper red, base will turn pH paper blue.

Q.6. How would you distinguish between baking powder and washing soda by heating?
Ans. 

  • Baking powder is NaHCO3 (sodium hydrogen carbonate).
  • It will produce CO2(g) on heating, which will turn lime water milky.
    2NaHCO3 NCERT Exemplar - Acids, Bases and Salts Notes | EduRevNa2CO3 + CO+ H2O
  • There will be no such gas evolved on heating washing soda (Na2CO3·10H2O).
  •  It will lose water of crystallization and become amorphous.
    Na2CO3.10H2ONCERT Exemplar - Acids, Bases and Salts Notes | EduRevNa2CO3 + 10H2O

Q.7. Salt A, commonly used in bakery products on heating, gets converted into another salt B, which itself is used for removal of hardness of water, and a gas C is evolved. The gas C, when passed through lime water, turns it milky. Identify A, B, and C.
Ans.
 

  • ‘A’ is sodium hydrogen carbonate.
    NCERT Exemplar - Acids, Bases and Salts Notes | EduRev
  • 'B' is sodium carbonate used for the removal of the hardness of water. 
  • The gas ‘C’ is carbon dioxide gas. When CO2 is passed through Lime water, it turns milky due to the formation of calcium carbonate.
    NCERT Exemplar - Acids, Bases and Salts Notes | EduRev

Q.8. In one of the industrial processes used for the manufacture of sodium hydroxide, a gas X is formed as a by-product. The gas X reacts with lime water to give a compound Y, which is used as a bleaching agent in the chemical industry. Identify X and Y giving the chemical equation of the reactions involved.
Ans.
Sodium chloride is used for manufacture of sodium hydroxide, which is called chloralkali process. In this process, chlorine and hydrogen gas are formed as byproducts along with sodium hydroxide. Chlorine gas gives bleaching power when reacts with lime water and used as a bleaching agent in chemical industries.
 2NaCl(aq)+2H2O(l) → 2NaOH(aq)+Cl2(g)+H2(g)
 X→Cl(Chlorine gas)
 Ca(OH)2+Cl⟶ CaOCl2+H2O
Therefore,
The gas X is chlorine.
Compound Y is calcium oxychloride which is commonly known as bleaching powder and used as a bleaching agent in chemical industries.

Q.9. Fill in the missing data in the following table
NCERT Exemplar - Acids, Bases and Salts Notes | EduRev
Ans.
NCERT Exemplar - Acids, Bases and Salts Notes | EduRev

Q.10. What are strong and weak acids? In the following list of acids, separate strong acids from weak acids.
Hydrochloric acid, citric acid, acetic acid, nitric acid, formic acid, sulphuric acid.

Ans.

  • Strong acids are those acids which are completely ionized in an aqueous solution.
    Example: H2SO4
  • Weak acids are those which do not ionize completely in an aqueous solution, Example: CH3COOH.
  • Strong acids: HCl, HNO3, H2SO4 
  • Weak acids: Citric acid, acetic acid, formic acid.

Q.11. When zinc metal is heated with a dilute solution of a strong acid, a gas is evolved hydrogenation oil. Name the gas evolved. Write the chemical equation of the reaction involved and also write a test to detect the gas formed.
Ans. When zinc metal is treated with a dilute solution of a strong acid, hydrogen gas is evolved.
 Zn + 2HCl → ZnCl2 + H2 
If we bring a burning splinter near the mouth of the test tube, the gas burns with a pop sound.

Long Answer Type Questions

Q.12. In the following schematic diagram for the preparation of hydrogen gas as shown in the given figure, what would happen if the following changes are made?NCERT Exemplar - Acids, Bases and Salts Notes | EduRev

(a) In place of zinc granules, the same amount of zinc dust is taken in the test tube.
(b) Instead of dilute sulphuric acid, dilute hydrochloric acid is taken.
(c) In place of zinc, copper turnings are taken.
(d) Sodium hydroxide is taken in place of dilute sulphuric acid, and the tube is heated.

Ans. 
(a) The reaction will become faster because zinc dust has more surface area.
(b) Nearly the same amount of hydrogen gas will be evolved.
(c) No reaction will take place as copper is less reactive than hydrogen.
(d) The reaction will take place, and hydrogen gas will be evolved.
NCERT Exemplar - Acids, Bases and Salts Notes | EduRev

Q.13. A metal carbonate X on reacting with an acid gives a gas which, when passed through a solution Y, gives the carbonate back. On the other hand, a gas G that is obtained at anode during electrolysis of brine is passed on dry Y, it gives a compound Z, used for disinfecting drinking water. Identify X, Y, G, and Z.
Ans.
 

  • ‘X' is calcium carbonate.
    NCERT Exemplar - Acids, Bases and Salts Notes | EduRev
  • 'Y’ is calcium hydroxide.
    NCERT Exemplar - Acids, Bases and Salts Notes | EduRev
  • The gas ‘G’ is chlorine gas, which is obtained at anode.
    NCERT Exemplar - Acids, Bases and Salts Notes | EduRev
  • ‘Z’ is calcium oxychloride used for disinfecting drinking water.

Q.14. A dry pellet of a common base B, when kept in the open, absorbs moisture and turns sticky. The compound is also a by-product of the Chlor-alkali process. Identify B. What type of reaction occurs when B is treated with an acidic oxide? Write a balanced chemical equation for one such solution.
Ans.
 

  • ‘B’ is NaOH.
  • It is obtained by-product of the Chlor-alkali process.
    NCERT Exemplar - Acids, Bases and Salts Notes | EduRev
  • ‘B ’ reacts with acidic oxide (CO2) to form salt and water. This reaction is called a neutralization reaction.

Q.15. A sulfate salt of Group 2 element of the Periodic Table is a white, soft substance, which can be molded into different shapes by making its dough. When this compound is left in the open for some time, it becomes a solid mass and cannot be used for molding purposes. Identify the sulfate salt. Why does it show such behaviour? Give the reaction involved.
Ans.
 

  • Salt is CaSO.1/2 H2O, Plaster of Paris, white soft substance. 
  • It can be dough, molded into different shapes, as 2 moles of CaSO4 share 1 mole of H2O molecule.
     CaSO4.1/2H2O + 3/2H2O → CaSO4.2H2O
  • When it is left in the open, it becomes solid mass CaSO4·2H2O (Gypsum), which cannot be used for molding purposes as it is a hard solid mass.

Q.16. Identify the compound X on the basis of the reactions given below. Also, write the name and chemical formula of A, B, and C.
NCERT Exemplar - Acids, Bases and Salts Notes | EduRev
Ans. ‘X ’ is NaOH.
NCERT Exemplar - Acids, Bases and Salts Notes | EduRev

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