💥CHAPTER-2
Acid Bases and Salts
Acids, Bases and Salts
Acids - Acids are compounds which give hydrogen ion in water solution. For example, Hydrochloric acid (HCl), Sulphuric acid(H2SO4), Nitric acid(HNO3).
Bases - Bases are compounds which give hydroxide ion in water solution. For example, Sodium hydroxide(NaOH), Potassium hydroxide(KOH), Calcium hydroxide( Ca(OH)2).
Salts - Salts are compounds obtained by replacement of H from acid by a metal. For example, Sodium chloride (NaCl), Copper sulphate (CuSO4), Potassium nitrate (KNO3).
General properties of Acids:
• Tastes sour
• Reacts with metals such as zinc, magnesium etc. liberating hydrogen gas.
• Changes the colour of litmus from blue to red.
• Conducts electricity.
General properties of Bases
• Have a soapy feel,
• May also burn the skin
• Common examples are soaps & detergents.
• Commonly found bases in laboratories and in our daily life are: Caustic soda, NaOH; Caustic
potash, KOH; Milk of magnesia, Mg(OH)2; Liquor ammonia, NH3; Washing powder, Tooth
paste
Strong and Weak -
- Strong acids ionize fully in water to produce large number of H+ ions. For example, Hydrochloric acid (HCl), Sulphuric acid(H2SO4), Nitric acid(HNO3), hydrobromic acid(HBr).
- Weak acids ionize partially in water to produce small number of H+ ions. For example, carbonic acid(H2CO3), phosphoric acid(H3PO4), sulphurous acid(H2SO3), acetic acid(CH3COOH).
- Strong bases ionize fully in water to produce large number of OH- ions. For example, sodium hydroxide (NaOH), potassium hydroxide (KOH), lithium hydroxide (LiOH), calcium hydroxide (Ca(OH)2).
- Weak bases ionize partially in water to produce small number of OH- ions. For example magnesium hydroxide (Mg(OH)2), ammonium hydroxide (NH4OH).
Concentrated and Dilute -
A concentrated solution is a solution in which large amount of solute is dissolved in less amount of water (solvent).
A dilute solution is a solution in which small amount of solute is dissolved in large amount of water (solvent).
Diluting Acids and Bases -
- If concentrated acid (or base) is mixed with water, concentration of hydronium ions () decreases. So the acid or base becomes dilute.
- The phenomena of changing concentrated acid / base into dilute acid / base (respectively) is an exothermic reaction.
- Always add concentrated acid/base to water; not water to concentrated acid/base.
- When concentrated acid is added to water, heat is released gradually. This heat is absorbed by large amount of water to increase its temperature.
- When water is added to concentrated acid, heat is released suddenly. This heat vaporizes small amount of water to steam. This steam is splits out with drops of concentrated acid which can damage our body. So always add concentrated acid to water, not water to concentrated acid.
- Same is true with base also.
INDICATORS :
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Indicators are substances which indicate the acidic or basic nature of the solution by their colour change. These are the substances which change their color/smell in different types of substances.
Indicators are substances which indicate the acidic or basic nature of the solution by their colour change. These are the substances which change their color/smell in different types of substances.
TYPES OF INDICATORS
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Universal Indicator: A universal indicator is a mixture of indicators which shows a gradual but well-marked series of color changes over a very wide range of change in concentration of H+ ion.
Hydronium Ions: They are formed by reaction of H+ (from acid) and H2O. It is because H+ is unstable..
pH scale : A scale for measuring hydrogen ion concentration in a solution. The pH of a solution is defined as the negative logarithm of hydrogen ion concentration in moles per liter.
pH =-log [H+]
pH =-log [H3O+]
where [H+] or [H3O+] represents concentrations of hydrogen ions in solution.
The pH of a neutral solution is 7
The pH of a acidic solution is < 7
The pH of a basic solution is > 7
-
-
Universal Indicator: A universal indicator is a mixture of indicators which shows a gradual but well-marked series of color changes over a very wide range of change in concentration of H+ ion.
Hydronium Ions: They are formed by reaction of H+ (from acid) and H2O. It is because H+ is unstable..
pH scale : A scale for measuring hydrogen ion concentration in a solution. The pH of a solution is defined as the negative logarithm of hydrogen ion concentration in moles per liter.
pH =-log [H+]
pH =-log [H3O+]
where [H+] or [H3O+] represents concentrations of hydrogen ions in solution.
The pH of a neutral solution is 7
The pH of a acidic solution is < 7
The pH of a basic solution is > 7
Substances pH value Saliva (before meal) 7.4 Saliva (after meal) 5.8 Lemon juice 2.5 Colourless aerated drink 6 Carrot juice 6 Coffee 5 Tomato juice 4.1 Tap water 6.8 1 M NaOH Conc. 14 1M HCl Conc. 0
pH of Salts :
-
- Strong Acid + Strong Base → Neutral Salt : pH = 7
- Salt of strong acid + Weak base → Acidic salt : pH < 7
- Salt of strong base + Weak acid → Basic salt : pH > 7
- Strong Acid + Strong Base → Neutral Salt : pH = 7
- Salt of strong acid + Weak base → Acidic salt : pH < 7
- Salt of strong base + Weak acid → Basic salt : pH > 7
Some Important Compounds and their uses
Common Name Chemical name Chemical formula Uses Washing soda Sodium carbonate decahydrate Na2CO3.10H2O Manufacture of borax, caustic soda, softening of hard water Baking soda Sodium hydrogen carbonate NaHCO3 Used as antacid, ingredient of baking powder Bleaching powder Calcium oxychloride CaOCl2 Bleaching clothes, used as oxidizing agent, disinfecting water, manufacture of chloroform Plaster of Paris Calcium sulphate hemihydrate CaSO4 .1/2H2O Plastering fractured bones, making toys ,decorative materials ,statues
Neutralization Reaction -
An acid neutralizes a base when they react with each other and respective salt and water are formed.
Since in the reaction between acid and base both neutralize each other, hence it is also known as neutralization reaction.
Example:
- Sodium chloride and water are formed when hydrochloric acid reacts with sodium hydroxide (a strong base).
- In similar way, calcium chloride is formed along with water when hydrochloric acid reacts with calcium hydroxide (a base).
- Sodium sulphate and water are formed when sulphuric acid reacts with sodium hydroxide (a base).
- In similar way, when nitric acid reacts with sodium hydroxide, sodium nitrate and water are formed.
Note: The most important thing in whole process is that H+ and OH- ions combine to form H2O.
-
Reaction of acids with metal Oxides -
Metal oxide is a chemical compound that contains oxygen and one metal in its chemical formula. For example, copper oxide (CuO), sodium oxide (Na2O), magnesium oxide (MgO).
Acids give water along with respective salt when they react with a metal oxide.
Metal + acid Respective salt + Water
Example :
- Water and sodium chloride are formed when hydrochloric acid reacts with sodium oxide.
Na2O + 2HCl (aq) 2NaCl + H2O
- Water and magnesium chloride are formed when hydrochloric acid reacts with magnesium oxide.
MgO + 2HCl MgCl2 + H2O
- Water and copper sulphate are formed when copper oxide reacts with sulphuric acid.
CuO + H2SO4 (aq) CuSO4 + H2O
- Water and copper chloride are formed when copper oxide reacts with hydrochloric acid.
CuO + 2HCl (aq) CuCl2 + H2O
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Reaction of bases with non - metal Oxides -
Non - metal oxide is a chemical compound that contains oxygen and one non - metal in its chemical formula. For example, carbon dioxide (CO 2), sulphur dioxide (SO 2).
When a base reacts with non-metal oxide both neutralize each other resulting respective salt and water are produced.
Base + non – metal oxide Respective salt + water
Example :
- Sodium hydroxide gives sodium carbonate and water when it reacts with carbon dioxide.
- Calcium hydroxide gives calcium carbonate and water when it reacts with carbon dioxide.
Note :
- When an acid reacts with a metal oxide, both neutralize each other. In this reaction, respective salt and water are formed as we saw in neutralization reaction. So it can be said that metal oxide are basic in nature.
- Similarly when a base reacts with a non – metal oxide, both neutralize each other. In this reaction, respective salt and water are formed. So it can be said that non - metal oxide are acidic in nature.
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Reaction of acids with metal -
Acids give hydrogen gas along with respective salt when they react with a metal.
Example:
- Hydrogen gas and zinc chloride are formed when hydrochloric acid reacts with zinc metal.
- Hydrogen gas and sodium chloride are formed when hydrochloric acid reacts with sodium metal.
- Hydrogen gas and iron chloride are formed when hydrochloric acid reacts with iron.
- Hydrogen gas and zinc sulphate are formed when zinc metal reacts with sulphuric acid
Note: Acid is not stored in metallic containers as acids and metals can easily react.
-
Reaction of Base with Metals -
When base reacts with metal, it produces salt and hydrogen gas.
Example:
- Sodium hydroxide gives hydrogen gas and sodium zincate when reacts with zinc metal.
- Sodium aluminate and hydrogen gas are formed when sodium hydroxide reacts with aluminium metal.
Note : Not all metals do this type of reaction.
-
Making Other Chemical from Common Salt -
Sodium Hydroxide -
- Sodium hydroxide is a strong base. It is also known as caustic soda or Iye.
- It is obtained by the electrolytic decomposition of solution of sodium chloride (brine).
- In the process of electrolytic decomposition of brine (aqueous solution of sodium chloride), brine decomposes to form sodium hydroxide.
- In this process, chlorine is obtained at anode and hydrogen gas is obtained at cathode as byproducts. This whole process is known as Chlor-Alkali process.
Use of products after the electrolysis of brine:
Hydrogen gas is used as fuel, margarine, in making of ammonia for fertilizer, etc.
Chlorine gas is used in water treatment, manufacturing of PVC, disinfectants, CFC, pesticides. It is also used in manufacturing of bleaching powder and hydrochloric acid.
Sodium hydroxide is used in de-greasing of metals, manufacturing of paper, soap, detergents, artificial fibres, bleach, etc.
Bleaching Powder (CaOCl 2) -
Bleaching powder is also known as chloride of lime. It is a solid and yellowish white in colour. Bleaching powder can be easily identified by the strong smell of chlorine.
When calcium hydroxide (slaked lime) reacts with chlorine, it gives calcium oxychloride (bleaching powder) and water is formed.
Water solution of bleaching powder is basic in nature.
The term bleach means removal of colour. Bleaching powder is often used as bleaching agent. It works because of oxidation. Chlorine in the bleaching powder is responsible for bleaching effect.
Use of bleaching powder:
- Bleaching powder is used as disinfectant to clean water, moss remover, weed killers, etc.
- Bleaching powder is used for bleaching of cotton in textile industry, bleaching of wood pulp in paper industry.
- Bleaching powder is used as oxidizing agent in many industries, such as textiles industry, paper industry, etc.
Baking Soda (NaHCO 3) -
Baking soda is another important product which can be obtained using byproducts of chlor-alkali process. The chemical name of baking soda is sodium hydrogen carbonate (NaHCO 3) or sodium bicarbonate. Bread soda, cooking soda, bicarbonate of soda, sodium bicarb, bicarb of soda or simply bicarb, etc. are some other names of baking soda.
Baking soda is obtained by the reaction of brine with carbon dioxide and ammonia. This is known as Solvay process.
In this process, calcium carbonate is used as the source of CO2 and the resultant calcium oxide is used to recover ammonia from ammonium chloride.
Properties of sodium bicarbonate:
- Sodium bicarbonate is white crystalline solid, but it appears as fine powder
- Sodium hydrogen carbonate is amphoteric in nature
- Sodium hydrogen carbonate is sparingly soluble in water
- Thermal decomposition of sodium hydrogen carbonate (baking soda)
- When baking soda is heated, it decomposes into sodium carbonate, carbon dioxide and water
Sodium carbonate formed after thermal decomposition of sodium hydrogen carbonate; decomposes into sodium oxide and carbon dioxide on further heating.
This reaction is known as dehydration reaction.
Use of Baking Soda:
- Baking soda is used in making of baking powder, which is used in cooking as it produces carbon dioxide which makes the batter soft and spongy.
- Baking soda is used as antacid.
- Baking soda is used in toothpaste which makes the teeth white and plaque free.
- Baking soda is used in cleansing of ornaments made of sliver.
- Since, sodium hydrogen carbonate gives carbon dioxide and sodium oxide on strong heating, thus it is used as fire extinguisher.
Baking powder -
Baking powder produces carbon dioxide on heating, so it is used in cooking to make the batter spongy. Although baking soda also produces carbon dioxide on heating, but it is not used in cooking because on heating; baking soda produces sodium carbonate along with carbon dioxide. The sodium carbonate; thus produced; makes the taste bitter.
Baking powder is the mixture of baking soda and a mild edible acid. Generally, tartaric acid is mixed with baking soda to make baking powder.
When baking powder (mixture of baking soda and an edible acid) is heated, the sodium carbonate formed because of heating of baking soda neutralizes after reacting with tartaric acid and sodium tartarate salt is formed. The smell of sodium tartarate is pleasant and taste is good. This makes the cake or any other food tasty.
Washing Soda (Sodium carbonate) -
Sodium carbonate is manufactured by the thermal decomposition of sodium hydrogen carbonate obtained by Solvay process.
The sodium carbonate obtained in this process is dry. It is called soda ash or anhydrous sodium carbonate. Washing soda is obtained by rehydration of anhydrous sodium carbonate.
Since there are 10 water molecules in washing soda, hence it is known as Sodium bicarbonate decahydrate.
Sodium carbonate is a crystalline solid and it is soluble in water when most of the carbonates are insoluble in water.
Use of sodium carbonate:
- It is used in cleaning of cloths; especially in rural areas.
- In making of detergent cake and powder.
- In removing permanent hardness of water.
- It is used in glass and paper industries.
Base & Alkali - Alkalis are water soluble bases.
Bases in which complete dissociation of hydroxide ion takes place are called strong base. In alkali; complete dissociation of hydroxide ions takes place so they are considered as strong base.
But it is not perfectly well defined that which substance is consider in category of Alkali and which is not.
| Common Name | Chemical name | Chemical formula | Uses |
| Washing soda | Sodium carbonate decahydrate | Na2CO3.10H2O | Manufacture of borax, caustic soda, softening of hard water |
| Baking soda | Sodium hydrogen carbonate | NaHCO3 | Used as antacid, ingredient of baking powder |
| Bleaching powder | Calcium oxychloride | CaOCl2 | Bleaching clothes, used as oxidizing agent, disinfecting water, manufacture of chloroform |
| Plaster of Paris | Calcium sulphate hemihydrate | CaSO4 .1/2H2O | Plastering fractured bones, making toys ,decorative materials ,statues |
Neutralization Reaction -
An acid neutralizes a base when they react with each other and respective salt and water are formed.
Since in the reaction between acid and base both neutralize each other, hence it is also known as neutralization reaction.
Example:
- Sodium chloride and water are formed when hydrochloric acid reacts with sodium hydroxide (a strong base).
- In similar way, calcium chloride is formed along with water when hydrochloric acid reacts with calcium hydroxide (a base).
- Sodium sulphate and water are formed when sulphuric acid reacts with sodium hydroxide (a base).
- In similar way, when nitric acid reacts with sodium hydroxide, sodium nitrate and water are formed.
Note: The most important thing in whole process is that H+ and OH- ions combine to form H2O.
Reaction of acids with metal Oxides -
Metal oxide is a chemical compound that contains oxygen and one metal in its chemical formula. For example, copper oxide (CuO), sodium oxide (Na2O), magnesium oxide (MgO).
Acids give water along with respective salt when they react with a metal oxide.
Metal + acid Respective salt + Water
Example :
- Water and sodium chloride are formed when hydrochloric acid reacts with sodium oxide.
Na2O + 2HCl (aq) 2NaCl + H2O
- Water and magnesium chloride are formed when hydrochloric acid reacts with magnesium oxide.
MgO + 2HCl MgCl2 + H2O
- Water and copper sulphate are formed when copper oxide reacts with sulphuric acid.
CuO + H2SO4 (aq) CuSO4 + H2O
- Water and copper chloride are formed when copper oxide reacts with hydrochloric acid.
CuO + 2HCl (aq) CuCl2 + H2O
Reaction of bases with non - metal Oxides -
Non - metal oxide is a chemical compound that contains oxygen and one non - metal in its chemical formula. For example, carbon dioxide (CO 2), sulphur dioxide (SO 2).
When a base reacts with non-metal oxide both neutralize each other resulting respective salt and water are produced.
Base + non – metal oxide Respective salt + water
Example :
- Sodium hydroxide gives sodium carbonate and water when it reacts with carbon dioxide.
- Calcium hydroxide gives calcium carbonate and water when it reacts with carbon dioxide.
Note :
- When an acid reacts with a metal oxide, both neutralize each other. In this reaction, respective salt and water are formed as we saw in neutralization reaction. So it can be said that metal oxide are basic in nature.
- Similarly when a base reacts with a non – metal oxide, both neutralize each other. In this reaction, respective salt and water are formed. So it can be said that non - metal oxide are acidic in nature.
- Reaction of acids with metal -Acids give hydrogen gas along with respective salt when they react with a metal.Example:
- Hydrogen gas and zinc chloride are formed when hydrochloric acid reacts with zinc metal.
- Hydrogen gas and sodium chloride are formed when hydrochloric acid reacts with sodium metal.
- Hydrogen gas and iron chloride are formed when hydrochloric acid reacts with iron.
- Hydrogen gas and zinc sulphate are formed when zinc metal reacts with sulphuric acid
Note: Acid is not stored in metallic containers as acids and metals can easily react. - Reaction of Base with Metals -When base reacts with metal, it produces salt and hydrogen gas.Example:
- Sodium hydroxide gives hydrogen gas and sodium zincate when reacts with zinc metal.
- Sodium aluminate and hydrogen gas are formed when sodium hydroxide reacts with aluminium metal.
Note : Not all metals do this type of reaction. - Making Other Chemical from Common Salt -Sodium Hydroxide -
- Sodium hydroxide is a strong base. It is also known as caustic soda or Iye.
- It is obtained by the electrolytic decomposition of solution of sodium chloride (brine).
- In the process of electrolytic decomposition of brine (aqueous solution of sodium chloride), brine decomposes to form sodium hydroxide.
- In this process, chlorine is obtained at anode and hydrogen gas is obtained at cathode as byproducts. This whole process is known as Chlor-Alkali process.
Use of products after the electrolysis of brine:Hydrogen gas is used as fuel, margarine, in making of ammonia for fertilizer, etc.Chlorine gas is used in water treatment, manufacturing of PVC, disinfectants, CFC, pesticides. It is also used in manufacturing of bleaching powder and hydrochloric acid.Sodium hydroxide is used in de-greasing of metals, manufacturing of paper, soap, detergents, artificial fibres, bleach, etc.Bleaching Powder (CaOCl 2) -Bleaching powder is also known as chloride of lime. It is a solid and yellowish white in colour. Bleaching powder can be easily identified by the strong smell of chlorine.When calcium hydroxide (slaked lime) reacts with chlorine, it gives calcium oxychloride (bleaching powder) and water is formed.Water solution of bleaching powder is basic in nature.The term bleach means removal of colour. Bleaching powder is often used as bleaching agent. It works because of oxidation. Chlorine in the bleaching powder is responsible for bleaching effect.Use of bleaching powder:- Bleaching powder is used as disinfectant to clean water, moss remover, weed killers, etc.
- Bleaching powder is used for bleaching of cotton in textile industry, bleaching of wood pulp in paper industry.
- Bleaching powder is used as oxidizing agent in many industries, such as textiles industry, paper industry, etc.
Baking Soda (NaHCO 3) -Baking soda is another important product which can be obtained using byproducts of chlor-alkali process. The chemical name of baking soda is sodium hydrogen carbonate (NaHCO 3) or sodium bicarbonate. Bread soda, cooking soda, bicarbonate of soda, sodium bicarb, bicarb of soda or simply bicarb, etc. are some other names of baking soda.Baking soda is obtained by the reaction of brine with carbon dioxide and ammonia. This is known as Solvay process.In this process, calcium carbonate is used as the source of CO2 and the resultant calcium oxide is used to recover ammonia from ammonium chloride.Properties of sodium bicarbonate:- Sodium bicarbonate is white crystalline solid, but it appears as fine powder
- Sodium hydrogen carbonate is amphoteric in nature
- Sodium hydrogen carbonate is sparingly soluble in water
- Thermal decomposition of sodium hydrogen carbonate (baking soda)
- When baking soda is heated, it decomposes into sodium carbonate, carbon dioxide and water
Sodium carbonate formed after thermal decomposition of sodium hydrogen carbonate; decomposes into sodium oxide and carbon dioxide on further heating.This reaction is known as dehydration reaction.Use of Baking Soda:- Baking soda is used in making of baking powder, which is used in cooking as it produces carbon dioxide which makes the batter soft and spongy.
- Baking soda is used as antacid.
- Baking soda is used in toothpaste which makes the teeth white and plaque free.
- Baking soda is used in cleansing of ornaments made of sliver.
- Since, sodium hydrogen carbonate gives carbon dioxide and sodium oxide on strong heating, thus it is used as fire extinguisher.
Baking powder -Baking powder produces carbon dioxide on heating, so it is used in cooking to make the batter spongy. Although baking soda also produces carbon dioxide on heating, but it is not used in cooking because on heating; baking soda produces sodium carbonate along with carbon dioxide. The sodium carbonate; thus produced; makes the taste bitter.Baking powder is the mixture of baking soda and a mild edible acid. Generally, tartaric acid is mixed with baking soda to make baking powder.When baking powder (mixture of baking soda and an edible acid) is heated, the sodium carbonate formed because of heating of baking soda neutralizes after reacting with tartaric acid and sodium tartarate salt is formed. The smell of sodium tartarate is pleasant and taste is good. This makes the cake or any other food tasty.Washing Soda (Sodium carbonate) -Sodium carbonate is manufactured by the thermal decomposition of sodium hydrogen carbonate obtained by Solvay process.The sodium carbonate obtained in this process is dry. It is called soda ash or anhydrous sodium carbonate. Washing soda is obtained by rehydration of anhydrous sodium carbonate.Since there are 10 water molecules in washing soda, hence it is known as Sodium bicarbonate decahydrate.Sodium carbonate is a crystalline solid and it is soluble in water when most of the carbonates are insoluble in water.Use of sodium carbonate:- It is used in cleaning of cloths; especially in rural areas.
- In making of detergent cake and powder.
- In removing permanent hardness of water.
- It is used in glass and paper industries.
Base & Alkali - Alkalis are water soluble bases.Bases in which complete dissociation of hydroxide ion takes place are called strong base. In alkali; complete dissociation of hydroxide ions takes place so they are considered as strong base.But it is not perfectly well defined that which substance is consider in category of Alkali and which is not.
very nice notes
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