Acids, Bases and salts BY TRI SIR.pptx

#Cbse 10 #Chemistry

1. Acids, Bases and salts CHAPTER- 2 SCINCE (CBSE CLASS 10) By: Tripurari Prajapati M.sc . Biotechnology

2. Elements are combined to form compounds. On the basis of their chemical properties, all the compounds will be classified into three types : 1 ) Acids : Sour in taste 2 ) Bases : Bitter in taste 3 ) Salts

3. Indicators for testing acids and bases : An indicator is a dye that changes color when it is put into an acid or a base. It tells us whether the substance we are testing is an acid or base.

4. TYPES OF INDICATORS Natural Indicators Synthetic Indicators Eg : a) Litmus Eg : a) Methyl orange b) Turmeric b) Phenolphthalein

5. Litmus : Litmus is a most common indicator used for testing acids and bases in the laboratory. Litmus can be used in the form of litmus paper or litmus solution. It is of two types : Blue litmus and Red litmus.

6. An acid turns blue litmus to red. A base (or alkali) turns red litmus to blue. A neutral No color change

7. If a drop of the given solution turns blue litmus to red, then the given solution will be acidic in nature. Ex. Orange juice turns blue litmus to red, so orange juice is acidic in nature. If drop of the given solution turns red litmus to blue. Then given solution will be basic in nature. Ex. NaOH solution.

8. Methyl orange : Methyl orange is synthetic indicator. The neutral colour of methyl orange is ‘orange ’. ( i) Methyl orange gives red colour in acidic solution. ( ii) Methyl orange gives yellow colour in basic solution.

9. Phenolphthalein : The neutral colour of phenolphthalein is colourless . The colour changes which take place in phenolphthalein indicator as below : (i) Phenolphthalein indicator is colourless in acid solution. (ii) Phenolphthalein indicator gives pink colour in basic solution.

10. Some natural indicators : Litmus Litmus is a natural indicator. Litmus solution is a purple dye which is extracted from a type of plant called ‘lichen’ Lichen is a plant belonging to the division Thallophyta . When litmus solution is neither acidic nor basic (it is neutral), then its colour is purple.

11. 2. Turmeric: Turmeric is also a natural indicator. Turmeric contains yellow dye. It turns red in basic solutions.

12. 3. The red cabbage: The red cabbage extract (obtained from red cabbage leaves) is also a natural indicator. It is red in colour . The red cabbage extract remains red in acidic solution but turns green on adding to basic solutions.

13. 4. Coloured petals of some flowers: The coloured petals of some flowers (such as Hydrangea, Petunia and Geranium ) which change colour in the presence of acids or bases also act as indicators. For example, the flower of Hydrangea plant are usually blue which turn pink in the presence of base.

14. Olfactory indicators : The term ‘olfactory’ means ‘relating to the sense of smell’. Those substances whose smell (or odour ) changes in acidic or basic solutions are called olfactory indicators. An olfactory indicator usually works on the principle that when an acid or base is added to it, then its ‘characteristic smell’ cannot be detected.

15. 1. Onion Onion has a characteristic smell . When a basic solution like NaOH is added to a cloth strip treated with onions, then the onion smell cannot be detected. An acidic solution like HCl does not destroy the smell of onions. This can be used as a test for acids and bases.

16. 2. Vanilla Vanilla extract has a characteristic pleasant smell. If a basic solution like NaOH is added to vanilla extract, then we cannot detect the characteristic smell of vanilla extract. An acidic solution like HCl does not destroy the smell of vanilla extract. This can be used as a test for acids and bases.

17. Sample problem : You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution, respectively. If you are given only red litmus paper, how will you identify the contents of each test-tube?

18. Acids Acids are those chemical substances which have a sour taste. Acids change the colour of blue litmus to red. Some common fruits such as raw mango, raw grapes, lemon, orange and tamarind ( imli ) etc. are sour in teste due to presence of acid.

19. Organic Acids : The acids present in plant material and animals are called organic acids. Organic acids are naturally occurring acids. Organic acids are weak acids . It does not harmful to eat or drink substances containing naturally occurring acids in them.

20. Sources of organic acids : Acid Sources Acetic acid Vinegar ( sirka ) Citric acid Lemon, orange Lactic acid Curd Tartaric acid Tamarind, unripe grapes Oxalic acid Tomato Formic acid ( methanoic acid) Ant sting, nettle leaf sting

21. Mineral acids: Mineral acids are man made acids . The three most common mineral acids are : Hydrochloric acid Sulphuric acid Nitric acid Concentrated mineral acids are very dangerous . They can burn our hands and clothes. Dilute acids are less harmful to us.

22. Concentrated and Dilute acids : A concentrated acid is one which contains the minimum possible amount of water. Dilute acid is one which contains much more of water in it. The concentration of an acid is decreased by adding more water to it.

23. Diluting Acids : The dilution of a concentrated acid should always be done by adding concentrated acid to water gradually with stirring and not by adding water to concentrated acid. This is because, when concentrated acid is added to water for preparing a dilute acid, then the heat is evolved gradually and easily absorbed by the large amount of water .

24. If, water is added to concentrated acid to dilute it, then a large amount of heat is evolved at once. This heat changes some of the water to steam explosively which can splash the acid on our face or clothes and cause acid burns.

25. Properties of acids : Acids have a sour taste. Acid turns blue litmus to red. Acid solutions conduct electricity. When an acid dissolved in water, we get the acid solution. The solution of all the acids conduct electricity.

26. Reaction with metal when an acid reacts with a metal, then salt and hydrogen gas are formed. For example, when dilute sulphuric acid reacts with zinc metal then zinc sulphate and hydrogen gas are formed.  

27. The reaction is carried out as follows : Take a few pieces of zinc granules in boiling tube and add 5ml of dil. Sulphuric acid to it. We will observe the formation of bubbles on the surface of zinc granules. Pass the gas being formed through the soap solution taken in a trough. Gas filled bubbles are formed in the soap solution which rise into the air.

28. Bring a burning candle near a gas filled soap bubbles. The gas present in soap bubble burns with the pop sound. Only hydrogen gas burns making a pop sound. This shows that hydrogen gas is evolved during reaction.

29. Example 2 : Dilute hydrochloric acid reacts with zinc to form zinc chloride and hydrogen gas. Note : Curd and other sour foodstuffs such as vinegar, lemon juice and orange juice, etc., should not be kept in metal vessels (like copper vessels or brass vessels) This is because foodstuffs contains acids which can react with metal and forms poisonous metal compounds.  

30. Reaction with metal carbonate When an acid reacts with a metal carbonate (or metal hydrogen carbonate), then a salt, carbon dioxide and water are formed.  

31. Example 1 : When dilute hydrochloric acid reacts with sodium carbonate, then sodium chloride, carbon dioxide and water are formed.  

32. This reaction can be performed as follows : Take a boiling tube and put about 0.5g of sodium carbonate in it. Add about 2mL of dilute hydrochloric acid in the boiling tube We will observe that brisk effervescence of a gas is produced. Pass the gas through lime water. The lime water turns milky.

33. Carbon dioxide gas reacts with lime water as follows : When carbon dioxide gas is passed through lime water, the lime water turns milky due to formation of a white PPT of calcium carbonate . If excess of carbon dioxide gas is passed through lime water, then white PPT formed first dissolves due to formation of soluble salt calcium hydrogen carbonate.  

34. Example 2 : When dilute hydrochloric acid reacts with sodium hydrogen carbonate , then sodium chloride, carbon dioxide and water are formed. Note : If someone is suffering from the problem of acidity after overcoming, we can suggest taking baking soda solution as remedy. Because baking soda is sodium hydrogen carbonate which reacts with excess HCl in the stomach and neutralizes it.  

35. Reaction with Base When an acid reacts with a base, then a salts and water are formed. When an acid is treated with a base, the base neutralizes the acid and destroys its acidity. So the reaction between an acid and base to form salt and water is called ‘ neutralization reaction ’.  

36. Example 1 : When hydrochloric acid reacts with sodium hydroxide solution, then a neutralization reaction takes place to form sodium chloride and water. Take about 5mL of dilute sodium hydroxide solution in a test tube (or a conical flask). Add 2 or 3 drops of phenolphthalein indicator. The solution will turn pink .  

37. Add dilute HCl to above NaOH solution dropwise and shake the test tube after each addition. After adding a certain volume of HCl , we will find that the pink colour of solution in the test tube just disappears. The solution becomes colourless . At this stage all the NaOH base taken in the test tube completely neutralized.

38. Reaction with metal oxides Acids react with metal oxides to form salt and water : Copper (II) oxide is a metal oxide. Dilute hydrochloric acid reacts with copper ( ll ) oxide to form copper ( ll ) chloride and water.  

39. Take a small amount of copper(ii) oxide in a beaker. It is black in colour . Take a small amount of copper(ii) oxide in a beaker. It is black in colour . Add dilute HCl slowly while stirring with a glass rod. We will find that copper( ll ) oxide has dissolved in dilute HCl to form blue green solution.

40. Acids have corrosive nature The mineral acids cause severe burns on the skin and attack and eat up materials cloth, wood, metal structures and stonework, so they are said to be corrosive. Acids are never stored in metal containers because they gradually corrode and eat up the metal container. The strong bases such as NaOH are also very corrosive, and attack and destroy our skin.

41. WHAT DO ALL ACIDS HAVE IN COMMON : All the acids contain hydrogen . An acid is a substance which dissociates (or ionizes) on dissolving in water to produce hydrogen ions. For example, an aqueous solution of HCl dissociates to form hydrogen and chloride ions.  

42. Sulphuric acid shows acidic behaviour because it ionizes in aqueous solution to give Hydrogen ions and sulphate ions. Ionization of Nitric acid :  

43. Ionization of phosphoric acid : Ionization Acetic acid :  

44. The compounds such as glucose ( ) and alcohol ( ) also contain hydrogen but they do not show acidic character.   The aqueous solutions and glucose and alcohol do not show acidic character because their hydrogen does not separate out as hydrogen ions.

45. TO SHOW THAT ALL THE COMPOUND CONTAINING HYDROGEN ARE NOT ACID: Take solutions of hydrochloric acid, sulphuric acid, glucose and alcohol. All these are hydrogen containing compounds. Fix two iron nails on a rubber cork and place the cork in a beaker. Connect the nails to the two terminals of a 6 volts battery through a switch and a bulb.

46. Pour some dilute HCl or solution in the beaker and switch on the current. The bulb starts glowing. This shows that solution taken in beaker conducts electricity. Now take glucose or alcohol solution in the beaker and switch on the current. The bulb does not glow in this case.  

47. Distilled water does not conduct electricity because it does not contain any ionic compound dissolved in it. On the other hand rain water conducts electricity. Rain water while falling to the earth through the atmosphere, dissolves acidic gas carbon dioxide from air and forms carbonic acid ( ). Carbonic acid provides hydrogen ions and carbonate ions.  

48. Acids contain as cation and anion such as   in HCl, in , in in Since the cation present in acids is , this suggests that acids produce hydrogen ion in a solution, which responsible for their acidic properties .  

49. STRONG ACIDS : An acid which is completely ionized in water and thus produces a large amount of hydrogen ions is called strong acids . Ex . etc. The strong acids react very rapidly with other substances such as metals. Strong acids have a high electric conductivity.  

50. WEAK ACIDS : An acid which is partially ionized in water and thus produces a small amount of hydrogen ions is called weak acids. Ex . . Weak acids reacts quite slowly with other substances. Weak acids have weak electrical conductivity .  

51. Uses of Mineral Acids in Industry : Sulphuric acid is used in the manufacture of fertilisers , paints, dyes, chemicals, plastics, synthetic fibers, detergents, explosives and car batteries. Nitric acid is used for making fertilisers , explosives, dye and plastics. HCl is used for removing oxide film from steel objects. It is also used in dye-stuff, textile and food and leather industries.

52. BASES : The solutions of substances like caustic soda , lime ( choona ) and washing soda are bitter in taste, and soapy to touch (slippery to touch). They called bases. Thus bases are those chemical substances which have a bitter in taste. All the bases change the colour of red litmus to blue.

53. Bases are the chemical opposite of acid. When bases are added to acids, they neutralize the effect of acids. All the metal oxides and metal hydroxides are bases. Ex:- Sodium oxide ( ), S odium hydroxide ( ), Calcium oxide ( ), Calcium hydroxide [ ] Ammonium hydroxide ( ), Metal carbonates hydrogen carbonates are also considered to be bases because they neutralize the acids . EX .  

54. WATER SOLUBLE BASES : ALKALIS Those bases which dissolves in water without any chemical reaction are called alkalis, i.e a base which is soluble in water is called an alkali. Some common water soluble bases are : . The soluble bases are much more useful than insoluble bases because most of chemical reactions takes place only in aqueous solutions.  

55. WHAT DO ALL THE BASES HAVE IN COMMON : When a base is dissolved in water, it always produces hydroxide ions For example, sodium hydroxide is a base because it dissolves in water to produce hydroxide ions.   water

56. Potassium hydroxide is base which dissolves in water to give hydroxide ions.   Magnesium hydroxide is also a base which dissolves in water to produce hydroxide ions.   water water

57. STRONG BASES : A base which completely ionizes in water and thus produces a large amount of hydroxide ions is called strong base (or strong alkali). Eg :-  

58. WEAK BASES : A base which is partially ionized in water and thus produces a small amount of hydroxide ions is called a weak base. Eg :- .  

59. PROPERTIES OF BASES : Bases have bitter taste . Bases feel soapy to touch. Bases turn red litmus to blue . Bases conduct electricity in solution.

60. CHEMICAL PROPERTIES Bases react with some metals to form hydrogen gas. Bases react with acids to form salt and water.   Heat

61. Bases react with non- metal oxides to form salt and water.  

62. USES OF BASES : Sodium hydroxide is used in the manufacture of soap, paper and a synthetic fibre called rayon. Calcium hydroxide is used in the manufacture of bleaching powder. Magnesium hydroxide is used as an antacid to neutralize excess acid in the stomach.

63. Sodium carbonate is used as washing soda and for softening hard water. Sodium hydrogen carbonate is used as baking soda in cooking food, for making baking powder, as an antacids to cure indigestion and in soda-acid fire extinguishers

64. STRENGTH OF ACID AND BASE SOLUTIONS : Water is slightly ionized into hydrogen ions and hydroxide ions. In pure water the concentration of hydrogen ions and hydroxide ions are equal. Due to this, pure water is neither acidic nor basic, it is neutral.

65. Acids produce hydrogen ions in water. So when an acid is added to water, then the concentration of hydrogen ions in water increases. The solution of acid thus formed will have more of hydrogen ions, and it will be acidic in nature. In other words acidic solutions have excess of hydrogen ions.

66. Bases produce hydroxide ions in water. So, when a base is added to water, then the concentration of hydroxide ions in it increases. The solution formed by dissolving a base in water will have more hydroxide ions, and it will be basic in nature . In other words, the basic solutions have excess of hydroxide ions.

67. We have learnt in the previous section about dilution and decrease in the concentration of or ions in the solution.   Can we quantitatively find the amount of these ions present in the solution? Can we judge how strong a given acid or base is?

68. universal indicator We can do this by making use of universal indicator, which is a mixture of several indicators. The universal indicator shows different colours at different concentrations of hydrogen ions in a solution.

69. pH SCALE : A scale for measuring hydrogen ion concentration in a solution called pH scale. The p in pH stands for ‘ potenz ’ in German, meaning power. On the pH generally from 0 (very acidic) to 14 (very alkaline).

70. pH should be thought of simply as a number which indicates the acidic or basic nature of a solution. Higher the hydronium ion concentration, lower is the pH value. The pH of a neutral solution is 7. Value less than 7 on the pH scale represents an acidic solution

71. As the pH value increases from 7 to 14, it represents an increase in the ion concentration in the solution, that is, increase in the strength of alkali .   Generally paper impregnated with the universal indicator is used for measuring pH.

72. COLOURS PRODUCED BY UNIVERSAL INDICATOR AT VARIOUS pH VALUES: pH Colour pH Colour Dark red 8 Greenish blue 1 Red 9 Blue 2 Red 10 Navy blue 3 Orange red 11 Purple 4 Orange 12 Dark purple 5 Orange yellow 13 Violate 6 Greenish yellow 14 Violate 7 Green

73. pH VALUES OF SOME COMMON SUBSTANCES: S.NO Solution Colour of pH paper Approximate pH value Nature 1. Saliva (before meal) Light green 7.4 Base 2. Saliva (after meal) Pale yellow 5.8 Acid 3. Lemon juice Pink red 2.5 Acid 4. Colourless aerated drink Pale yellow 6 Acid 5. Carrot juice Light orange 4 Acid 6. Coffee Orange yellow 5 Acid 7. Tomato juice Dark orange 4.1 Acid 8. Tap water Green 7 Neutral 9. 1M NaOH Violate 13-14 Base 10. 1M HCl Red 1 Acid

74. Sample problem : You have two solutions A and B. The pH of solution A is 6 and pH of solution B is 8 (a ) Which solution has more hydrogen ion concentration? ( b) Which of the solutions is acidic and which one is basic? 2. Five solutions A,B,C,D and E when tested with universal indicator showed pH of 4,1,11,7 and 9 respectively, ( a)Which solution is (i) neutral, (ii)strongly alkaline, (iii)strongly acidic , (iv)weakly acidic, (v)weakly alkaline? ( b) Arrange pH in increasing order of hydrogen ion.

75. IMPORTANCE OF pH IN EVERYDY LIFE : pH in our Digestive system : Our stomach produces hydrochloric acid (of pH 1.4). This dilute HCl helps in digestion our food without harming the stomach. Sometimes, excess of acid is produced in the stomach due to various reasons.

76. The excess acid in the stomach causes indigestion which produces pain and irritation. To get rid of this pain people use bases called antacids. These antacids neutralize the excess acids. Magnesium hydroxide (milk of magnesia), a mild base is often used for this purpose.

77. 2) pH change as the cause of tooth decay: When we eat food containing sugar, then the bacteria present in our mouth break down the sugar to form acids. This acid lowers the pH in the mouth. Tooth decay starts when the pH of acid formed in the mouth falls below 5.5. Tooth is made up of calcium hydroxyapatite (crystalline form of calcium phosphate) is the hardest substance in the body.

78. It does not dissolve in water, but is corroded when the pH in the mouth is below 5.5. The best way to prevent tooth decay is to clean the mouth thoroughly after eating food. Many toothpastes contain bases. It can neutralize the excess acid in mouth and prevent tooth decay.

79. 3. Plant and animals are sensitive to pH changes : Our body works within the pH range 0f 7.0 to 7.8. Living organism can survive only in a narrow range of pH change. When pH of rain water is less than 5.6, it is called acid rain.

80. When acid rain flows into the rivers, it lowers the pH of the river water. The survival of aquatic life in such rivers becomes difficult. Calcium carbonate is often added to acidic lake water to neutralize the acid.

81. 4) What is the pH of the soil in your backyard? Most of the plant grow best when the pH of the soil is close to 7 If the soil is too acidic or too basic, the plant grow badly or do not grow at all. The soil may be acidic or basic naturally. The soil pH is also affected by the use of chemical fertilizers in the field.

82. The pH of acidic soil can reach as low as 4 and that of the basic soil can go up to 8.3. If the soil is too acidic then it is treated with materials like quicklime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate). If the soil is too alkaline then its alkalinity can be reduced by adding decaying organic matter (manure or compost) which contains acidic material.

83. The pH of acidic soil can reach as low as 4 and that of the basic soil can go up to 8.3. If the soil is too acidic then it is treated with materials like quicklime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate). If the soil is too alkaline then its alkalinity can be reduced by adding decaying organic matter (manure or compost) which contains acidic material.

84. We can check pH of a soil ourselves as follows: take about 2g soil in a test tube and add 5 mL of water to it. Shake the test tube well. Filter the contents of the test tube through a filter paper and collect the filtrate. Find the pH of this filtrate by using the universal indicator paper.

85. 5) Self defence by animals and plants through chemical warfare: Many animals and plants protect themselves from their enemies by injecting painful and irritating acids and bases into their skin. For example, when a honey bee stings a person, it injects an acidic liquid into the skin which causes immense pain and irritation.

86. v If the bee stings a person, then rubbing a mild base like baking soda solution on the stung area of the skin gives relief. When a wasp stings, it injects an alkaline liquid into the skin. So if a wasp stings a person, then rubbing a mild acid like vinegar on the stung area of the skin gives relief.

87. Some plants also give painful stings. For example, nettle is a herbaceous plant which grows in the wild. The nettle leaves have stinging hair. When a person happens to touch the leaves of a nettle plant accidently, the stinging hair of nettle leaves inject methanoic acid into the skin of the person causing burning pain. The nettle sting being acidic can be neutralized by rubbing baking soda.

88. Even nature itself has provided remedy for the nettle sting in the form of ‘dock’ plant. So, a traditional remedy for the nettle leaf sting is to rub the stung area of the skin of the person with the leaf of dock plant.

89. SALTS : A salt is a compound formed from an acid by the replacement of the hydrogen in the acid by a metal . In HCl if we replace the hydrogen (H) by metal atom, (Na), then we will get a salt NaCl. In some salts, however, the hydrogen pf acid is replaced by ammonium group as in the case of ammonium chloride.  

90. The salts if hydrochloric acids are called chlorides. The salts of sulphuric acid are called sulphates. The salts of nitric acid are called nitrates. The salts of carbonic acid are called carbonates. The salts of acetic acid are called acetates.

91. SOME IMPORTANT SALTS AND THEIR FORMULAE: SALT FORMULA SALT FORMULA Sodium chloride Zinc sulphate Calcium chloride Copper sulphate Magnesium chloride Ammonium sulphate Zinc chloride Sodium nitrate Sodium sulphate Potassium nitrate Potassium sulphate Sodium carbonate Calcium sulphate Calcium carbonate Magnesium sulphate Zinc carbonate Aluminium sulphate Sodium acetate SALT FORMULA SALT FORMULA Sodium chloride Zinc sulphate Calcium chloride Copper sulphate Magnesium chloride Ammonium sulphate Zinc chloride Sodium nitrate Sodium sulphate Potassium nitrate Potassium sulphate Sodium carbonate Calcium sulphate Calcium carbonate Magnesium sulphate Zinc carbonate Aluminium sulphate Sodium acetate

92. Properties of salt Salts are mostly solids. They have high melting points and boiling points. Salts are usually soluble in water. Just like acids and bases, solution of salts in water conduct electricity. Salt solution conducts electricity due to the presence of ions in them. Salts are ionic compounds .

93. FAMILY OF SALTS: The salts having the same positive ions (or negative ions) are said to belong to a family of salts. For example and belongs to the same family salts called sodium salts. Similarly and belong to the same family of salts called chloride salts.  

94. THE pH OF THE SALT SOLUTION: Salts of strong acid and a strong base are neutral with pH value of 7. Salts of strong acid and weak base are acidic with pH value less than 7. Salts of strong base and weak acid are basic in nature with pH value more than 7.

95. Salt pH Acid used Base used Sodium chloride 7 Potassium nitrate 7 Aluminium chloride 7 Zinc sulphate 7 Copper sulphate <7 Sodium acetate >7 Sodium carbonate >7 Sodium hydrogen carbonate >7 Salt pH Acid used Base used Sodium chloride 7 Potassium nitrate 7 Aluminium chloride 7 Zinc sulphate 7 Copper sulphate <7 Sodium acetate >7 Sodium carbonate >7 Sodium hydrogen carbonate >7

96. COMMON SALT (SODIUM CHLORIDE) : The common salt is white powder which is used in preparing food, especially vegetables and pulses. Common salt is known as just salt. The chemical name of common salt is sodium chloride. Common salt is a neutral salt.

97. Sodium chloride can be made in the laboratory by the combination of sodium hydroxide and hydrochloric acid. The sodium chloride solution formed here can be evaporated to obtain sodium chloride salt. But sodium chloride is never made in this way on a large scale. Because sodium chloride is present in nature in abundance.  

98. HOW COMMON SALT IS OBTAINED : Common salt from sea water : Sea water contains many dissolved salts in it. The major salt present in sea water is common salt. Common salt is obtained from sea water by the process of evaporation. This is done by as follows .

99. Sea water is trapped in large, shallow pools and allowed to stand there. The sun’s heat evaporates the water slowly and common salt is left behind. This salt is impure because it has some other salts mixed in it. It is purified to obtain pure common salt.

100. Common salts from underground deposits. The large crystals of common salts found in in underground deposits are called rock salt . Rock salt is usually brown due to the presence of impurities in it. Rock salt is mined from underground deposits just like coal.

101. USES OF COMMON SALT : The common salt thus obtained is an important raw material for various materials of daily use, such as sodium hydroxide, baking soda, washing soda, bleaching powder and many other more.

102. Sodium hydroxide : When electricity is passed through an aqueous solution of sodium chloride (called brine), it decomposes to form sodium hydroxide. The process is called the chlor-alkali process because of the products formed chlore for chlorine and alkali for sodium hydroxide.  

103. Chlorine gas is given off at the anode, hydrogen gas at the cathode. The three products produced in this process are all useful.

104. Bleaching powder : Chlorine gas is used for the manufacture of bleaching powder. Bleaching powder is produced by the action of chlorine on dry slacked lime . Bleaching powder is represented as .(calcium hypochloride )  

105. Bleaching powder is used : For bleaching cotton and linen in the textile industry , for bleaching wood pulp in paper factories and for bleaching washed clothes in laundry. As an oxidizing agent in many chemical industries. For disinfecting drinking water to make it free from germs.

106. Baking soda : The soda commonly used in the kitchen for making tasty crispy pakoras is baking soda. Sometimes it is added for faster cooking. The chemical name of the compound is sodium hydrogen carbonate. It is produced using sodium chloride as one of the raw material.  

107. Sodium hydrogen carbonate is a non-corrosive base . The following reaction takes place when it is heated during cooking   heat

108. Uses of sodium hydrogencarbonate : For making baking powder , which is a mixture of baking soda and a mild edible acid such as tartaric acid. When baking powder is heated or mixed in water , the following reaction takes place. produced during the reaction causes bread or cake to rise making them soft and spongy.  

109. Sodium hydrogen carbonate is also an ingredient in antacids . Being alkaline, it neutralizes excess acid in the stomach and provides relief. It is also used in soda-acid fire extinguishers.

110. Washing soda : Washing soda is obtained from sodium chloride. We have seen that sodium carbonate can be obtained by heating baking soda, crystallization of sodium carbonate gives washing soda. It is also a basic salt .  

111. Uses of washing soda : It is used in glass, soap and paper industries. It is used in the manufacture of sodium compounds such as borax. It can be used as a cleaning agent for domestic purposes. It is used for removing permanent hardness of water.

112. Plaster of paris : On heating gypsum at 273 K , it loses water molecules and becomes calcium sulphate hemihydrate . This is called plaster of Paris.   Heat Gypsum Plaster of Paris

113. Plaster of Paris is the substance which doctors use as a plaster for supporting fractured bones in the right position. Plaster of Paris is a white powder and on mixing with water, it changes to gypsum once again giving the hard solid mass.     Gypsum Plaster of Paris

114. Uses : Plaster of Paris is used for making toys materials for decoration and for making surface smooth .

115. Why calcium sulphate hemihydrate is called plaster of Paris? The name plaster of Paris is derived from the large deposits of gypsum in the ‘ Montmartre hill ’ in Paris.

116. THANK YOU