NCERT solutions class 10 chapter 2  Acids, Bases and Salts

Here we have provided NCERT solutions for class 10 chapter 2  Acids, Bases and Salts according to lattest pattern released by CBSE.

Before going to NCERT solutions for class 10 chapter 2  Acids, Bases and Salts. Let's have a look at the Quick Revision notes of  Class 10 Chapter 2 Acids, Bases and Salts

In Text Questions

Page no - 18

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

Answer:
Step-1   Add the litmus paper to all three test tube. The solution which turns the red litmus to blue will be basic soluttion.
Step-2 Now put the blue litmus paper obtained above in the remaining two test tubes. The solution which turn blue litmus paper to red is acidic solution.
Step-3 The solution which remains neutral to both litmus paper will be distilled water.

Page no - 22



Quick revision note of class 10 science
chapter 3 Acids, Bases and Salts

   

        ACIDS , BASES  AND SALTS 

On the basis of their chemical properties ,all the compounds classified into three groups.
1. Acids
2. Bases
3. Salts

INDICATOR FOR TESTING ACIDS & BASES:-

- An indicator is a dye that changes color when put into acid or a base.
- It gives different colors in acid and base. Thus it tells us whether the substance we are testing is acid or base.
Ex:-some most common indicator to test for acids and bases are litmus paper, methyl orange and phenolphthalein .

1. Litmus paper:-

- It is of two types (i) Blue litmus
                                 (ii) red litmus
- An acid turns blue litmus to red.
- A base turns red litmus to blue.

If a drop of 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 i.e orange juice contains acid.

If a drop of the given solution turns red litmus to blue, then the given solution will be basic in nature.
Ex:- Sodium Hydroxide solution turns red litmus to blue, so sodium hydroxide solution turns is basic in nature(Or alkaline in nature).

NOTE:-

What is alkali ?

Ans:-  water soluble base is called an alkali.

2. Methyl orange:-

- The neutral colors of methyl orange is orange. The colors change take place in methyl orange as follows.
(i) Methyl orange indicator give red color in acidic solution.
(ii) Methyl orange indicator give yellow color in basic solution.

3. Phenolphthalein:-

- The neutral color of phenolphthalein is “colorless”. The color changes which takes place in phenolphthalein  indicator as given below
(i) Phenolphthalein indicator is colorless in acidic solution.
(ii) Phenolphthalein indicator gives pink color in basic solution.

4.Olfactory indicators:-

The term “olfactory” means to the “sense of smell”.
- Those substances whose smell changes in acidic or basic solution are  called olfactory indicators.
Ex:- Onion has a chara cterstic smell .When  basic solution like sodium hydroxide solution is added to a cloth strip treated with onions, then the onion smell can not be detected.
An acidic solution like hydrochloric acid ,however doesn’t destroy the smell of onions. This can be used a test for acids and bases.

Vanilla extract has characteristics pleasant smell .If  a basic solution like sodium hydroxide solution  is added to vanilla extract, then we cannot detect the characteristic smell of vanilla extract , An acidic solution like hydrochloric acid however does not destroy the smell of vanilla extract. This can be used as a test for acids and bases.

ACIDS

- Acids are those chemical substances which have a  sour taste.
-  Acid changes the color of blue litmus to red.
Ex:- Lemon, orange, tamarind curd etc.

On the basis of occurrence the acids classified as follows

1.Organic acids:-

- The acids present in plant material and animals are called organic acids.
e.g.- Acetic acid ,citric acid lactic acid formic acid.
- It is not harmful to eat or drink substances containing naturally occurring acids  in them.
- Organic acid are weak acids.

2.Mineral acids:-

-The acids prepared from the minerals of the earth are called mineral acids.
Ex- HCL,H₂SO₄,HNO₃
-Concentrated mineral acids are very dangerous .They can burn our hands and cloths.
-Mineral acids are strong acids.

3.Concentrated acids:-

A concentrated acid is one which contain the minimum  possible of water in it.

4.Dilute acids:- 

A dilute acid is one which contain much more of water in it.
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.

PROPERTIES OF ACIDS:-

1. Acids have a sour taste.
2. Acids turn blue litmus to red.
3.Acids solution conduct electricity (They are electrolyte).
4.acids react with metal to from hydrogen gas.
  Acid   +    Metal  ->   salt      +   hydrogen gas
Ex:-  H₂SO₄(aq)  +   Zn(s)  ->  ZnSO₄(aq)  + H₂(g)
In this reaction zinc metal react with sulphuric acids to form zinc sulphate and hydrogen gas is dissolved.

NOTE:- Curd and other sour food stuffs such as vinegar, lemon juice and orange juice etc. should not be kept in metal vessel .Because they can react with metal of vessel to form  poisonous metal compounds which can cause food poisoning and damage our health.

5.  Acids react with metal carbonate and metal hydrogen carbonate to form carbon dioxide gas.
Metal carbonate + Acid  ->    salt  +     CO2  +H2O
When dilute HCL react with sodium carbonate then sodium chloride ,carbon dioxide and water are formed.
NaHCO₃(s) + HCl(aq) -> NaCl(aq) + CO₂(g) + H₂O(l)

6.Acids react with bases to form salt and water.
        Acid       +    Base   ->  Salt     +   water
When an acid is treated with base, the base neutralize the acid and destroys its acidity. Since acid and base neutralize each other , so the reaction between acid and base to form salt and water is called neutralization.
Ex:-When hydrochloric acid react with sodium hydroxide , then a neutralization  reaction take place to form sodium chloride and water.
 NaOH(aq) + HCl(aq) -> NaCl(aq)   +  H₂O(l)

7.Acids react with metal oxides to from salt and water.
Metal  oxide   +  Acid   ->  Salt     +    water
Ex:-Copper(II) oxide is a metal oxide , reacts with dilute Hydrochloric acid to Copper (II) chloride and water.
  CuO(s)  + 2HCl(aq) ->CuCl₂(aq) +  H₂O(l)

8 . Acids have corrosive nature :- The mineral acids cause  severe burns on the skin and attack and eat up the material like cloth , wood , metal structures and stone work.

What do all acids have in common :-

-Hydrogen present in acids is such that when acids is dissolved in water , it separate out as positively charged hydrogen ions(H⁺).
-We can now define an acid on the basis hydrogen ions (H⁺) as  "An acid is a substance which dissociate on dissolving in water to produce hydrogen ions (H⁺)" .
Ex:- An aqueous solution of hydrochloric acid  dissociate to hydrogen ions.
HCl(aq)  ->   H⁺(aq)   +    Cl^-(aq)

-The aqueous solution of glucose and alcohol do not show acidic character because their hydrogen does not separate out as hydrogen ions (H⁺)on dissolving in water.
- From this we conclude that though all the acids contains hydrogen but all the hydrogen containing compounds are not acids.

STRONG ACIDS:-

- An acid which is completely ionised in water and thus produces a large amount of hydrogen ions is called strong acid
Ex:- HCl, H₂SO₄, HNO₃ etc.
-Strong acid react very rapidly with other substance.

WEAK ACIDS:-

-An acid which partially ionized in water and thus produces a small amount of hydrogen ions is called a weak  acid.
Ex:-CH₃COOH, H₂CO₃,H₂SO₃
-Weak acid react quit slowly with other substances.

USE OF MINERAL ACIDS IN INDUSTRY:-

-Sulphuric acids is used in the manufacturing of fertilizers, paints, dyes chemicals, detergents, explosives etc.
-Hydrochloric acid is used for removing scale deposits from inside the boiler. It is also used in dye stuff, textile food and leather industries.

BASE

-Bases are those chemical substances which have a bitter in taste.
-Base change the color of red litmus  to blue.
-Base is a chemical substance which can neutralize an acid.
Ex: NaOH,CaO,NH₄OH,Na₂CO₃.
-A base is a soluble in water is called alkali.
-A base substance which dissolve in water to produce hydroxide ions(OH^-)in solutions.
         NaOH(s)  ->    Na⁺(aq)  +  OH⁺(aq)
   

STRONG BASE:

A base which completely ionised in water and thus produces a large amount of hydroxide ion (OH^-)
e.g.  NaOH ,KOH ,etc.

WEAK BASE:

A base which is partially ionised in water and thus produces a small amount of hydroxide ions(OH^-) is called a weak base.
Ex-NH₄OH , Ca(OH)₃ etc.

PROPERTIES OF BASE :

I.Bases have bitter taste.
II.Bases feel soapy to touch.
III.Bases turn red litmus to blue.
IV.Bases conduct electricity in solution (They are electrolyte).
V.Base react with some metals to form hydrogen gas.
   Ex: When sodium hydroxide solution is heated with zinc , then sodium zincate and hydrogen gas are formed.
    2NaOH +Zn (s)  ->   Na₂ZnO₂(aq)+H₂(g)

VI. Bases react with acids to form salt and water
Ex : When sodium hydroxide react with sulphuric acid then sodium sulphate and water are  formed.
2NaOH +  H₂SO₄    ->      Na2SO4  +  2H₂O

VII. Bases react with non metal oxide to form salt and water.
Ex: Calcium hydroxide react with Corban dioxide to form calcium carbonate and water.
Ca(OH)₂ +  CO₂   ->    CaCO₃+H₂O

USES OF BASES:

-Sodium hydroxide is used in the manufacture of soap, paper and a synthetic fiber called rayon.
-Calcium hydroxide is used in manufacturing of bleaching powder.

STRENGTH OF ACID AND BASE SOLUTIONS : PH SCALE

-In 1909 Sorenson devised a scale (PH scale )on which the strength of acide solution as well as basic solution could be represented by making use of the hydrogen ion concentration in them.
-The pH of a solution is inversely proportional to the concentration of hydrogen ions in them.
-A solution having high concentration of hydrogen ions have a low pH value .On the other hand, a solution having low concentration of hydrogen ion has High pH value.
-In the term 'pH', letter 'p' stands for a German word "potenz" which means 'power' and letter 'H' stands for hydrogen ions concentration (H⁺).
a) Neutral substances have a pH of exactly 7. Ex - Pure water, sugar solution etc.
b) Acids have a pH of less than 7.
Lower pH, stronger the acid.
Ex-Solution of pH  1 is more acidic than another solution of pH 4.
c)  Bases have  a pH  between 7 and 14.
Ex-solution of pH 14 will be much more basic than another solution of pH 10.

Importance of pH in every day life :

1.pH In our digestive system:

           Dil. Hydrochloric acid helps in digesting out food . The  excess acid in stomach  cause indigestion. Being basic in nature , antacids react with excess acid in stomach and neutralize it.

2. pH change as the cause of tooth decay:

The bacteria present in mouth break down the sugar to form acids. Tooth decay start when the pH of acid prevent tooth decay is to clean the mouth thoroughly after eating food.

3.Self defence by the animal and plant through the chemical warfare:

•When a honey bee stings a person ,it injects an acidic liquid into  the skin .which causes immenes pain and irritation.
•An ant is sting inject nethanoic acid into the skin of a person causing burning pain.

             SALTS

-A salt is a compound formed from an acid by the replacement of the hydrogen in the acid by a metal.
     e.g.- Hydrochloric acid is HCl. if we replace the hydrogen (H) of this acid by a metal  atom, say a sodium atom (Na), then we will get a salt NaCl (sodium chloride).                                                 Salts are formed when acids react with bases. In a way, the name of a salt consists of two parts: the first part of the name of salt is derived from the name of base, and the second part of the name of the salt comes from the name of acid. 
  e.g.- The name of a salt called 'sodium chloride comes from sodium hydroxide base an hydrochloric acid.

Family of Salts

The salts having the same positive ions (or same negative ions) are said to belong to a family of salts. For example, sodium chloride (NaCl) and sodium sulphate (Na₂SO₄) belong to the same family of salts called 'sodium salts' (because they both contain the same positively charged ions, sodium ions Na+.

The pH of salt solution

 The aqueous solutions of many salts are neutral having a pH of 7, but some salts produce acidic or basic solutions (alkaline solution) when dissolved in water.

 The acidic nature and basic nature of some salt solutions can be explained on the basis of hydrolysis of salts.
(i) The salts of strong acids and strong bases give neutral solutions (having pH = 7).
e.g. - Sodium chloride salt (NaCl) is formed from a strong acid hydrochloric acid (HCI), and a strong base sodium hydroxide (NaOH). Since sodium chloride is formed from a strong acid and a strong base, therefore, an aqueous solution of sodium chloride is neutral.
(ii) The salts of strong acids and weak bases give acidic solution (having pH less than 7).
e.g- Ammonium chloride (NH₄Cl) is the salt of a strong acid hydrochloric acid (HCI), and a weak base ammonium hydroxide (NH₂OH), so an aqueous solution of ammonium chloride is acidic in nature.
(iii) The salts of weak acids and strong bases give basic solutions (having pH more than 7).
e.g.- Sodium carbonate, Sodium carbonate (Na₂CO₃) is the salt of a weak acid carbonic acid (H₂CO₃) and a strong base sodium hydroxide (NaOH), so an aqueous solution of sodium carbonate will be basic in nature or alkaline in nature.

COMMON SALT (SODIUM CHLORIDE)

*The chemical name of common salt is sodium chloride (NaCl)
* Common salt (or sodium chloride) is a neutral salt.
* Sodium chloride can be made in the laboratory by the combination of sodium hydroxide and hydrochloric acid.

Use of Common Salt (or Sodium Chloride)

Some of the important uses of common salt (or sodium chloride) are
1. Common salt (sodium chloride) is used as a raw material for making a large number of useful chemicals in industry such as : sodium hydroxide (caustic soda), sodium carbonate (washing soda).
2. Common salt (sodium chloride) is used in cooking food. Sodium chloride is required by our body for the working of nervous system, the movement of muscles, and the production of hydrochloric acid in the stomach for the digestion of food.
3. Common salt (sodium chloride) is used as a preservative in pickles, and in curing meat and fish .
4. Common salt (sodium chloride) is used in the manufacture of soap.
5. Common salt (sodium chloride) is used to melt ice which collects on the roads during winter in cold countries.

CHEMICALS FROM COMMON SALT

The preparation and uses of some of the important chemicals (chemical compounds) which are     obtained from common salt (or sodium chloride) by various methods.

1. 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 chloro-alkali process because of the products formed–chloro for chlorine and alkali for sodium hydroxide.
2NaCl(aq) + 2H₂O(l) → 2NaOH(aq) + Cl2(g) + H2(g)

Uses of Sodium Hydroxide

i. Sodium hydroxide is used for making soaps and detergents.
ii. Sodium hydroxide is used for making artificial textile fibers (such as rayon).
iii. Sodium hydroxide is used in the manufacture of paper.

2. Bleaching powder-

 Bleaching powder is produced by the action of chlorine on dry slaked lime [Ca(OH)₂].
Bleaching powder is represented as CaOCl₂.
        Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O

Use of Bleaching powder

i. for bleaching cotton and linen in the textile industry, for bleaching wood pulp in paper     factories and for bleaching washed clothes in laundry.
ii. As an oxidising agent in many chemical industries.
iii. To make drinking water free from germs.

3. Baking soda 

The chemical name of the compound is sodiumhydrogencarbonate (NaHCO₃). Sodiumhydrogencarbonate is produced by reacting a cold and concentrated solution of sodium chloride (called brine) with ammonia and carbon dioxide.
 NaCl + NH₃ + CO₂ + H₂O      NaHCO₃ + NH₄Cl

Use of Baking soda

i. Sodiumhydrogencarbonate is also an ingredient in antacids. Being alkaline, it neutralizes excess acid in the stomach and provides relief.
ii. It is also used in soda-acid fire extinguishers.

4. Washing soda

 Sodium carbonate can be obtained by heating baking soda, recrystallization of sodium carbonate gives washing soda.
          Na2CO3 + 10H2O -> Na₂CO₃.10H₂O

Uses of washing soda

i. Sodium carbonate (washing soda) is used in glass, soap and paper industries.
ii. It is used in the manufacture of sodium compounds such as borax.
iii. Sodium carbonate can be used as a cleaning agent for domestic purposes.
iv. It is used for removing permanent hardness of water.

5. Plaster of Paris-

 On heating gypsum at 373 K, it loses water molecules and becomes
calcium sulphate hemihydrate (CaSO₄.1/2H₂O). This is called Plaster of Paris.

Uses of plaster of paris

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

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MATTER

 Anything which occupies space and has mass is called matter.
 In other word, anything which has mass and volume is called matter.
 Ex- chain, table, computer, book, pen, tree etc.
According to their physical and chemical properties, matters can be divided into three types
  (i) Solid
  (ii) liquid
  (iii)gas

PROPERTIES OF MATTER

 -Matter is made up of small particles.
 -These particles have spaces between them.
 - Particles of matter attract each other because of force of attraction.

EXPERIMENT

 1: EXPERIMENT WITH POLLEN GRAINS

- If we suspend extremely small ,pollen grains in water and see though microscope, we found that the tiny particle of water do collision with
pollen grains.
- Due to these collision pollen grains move slightly.

 2: MIXING OF INK WITH WATER

 -If we put a drop of ink water, we see that initially ink is present in small
 That initially ink is present in small portion of water and after sometime,ink
 Spread up all over in the water.
 -This happen because the tiny particles of water collide with tiny particles of Ink .Due to this collision, particle of water and ink mix with each other.

 From above two experiment, its is proved that
➢ Matter is made up of tiny particles.
➢ Particles do Brownian motion.

Brownian motion of dust particle and smoke

→ Mr. Robert Brownian observed the random movement of pollen grains in water in 1872, this movement of particle is called Brownian motion.
→ Dust move randomly because the random moving particle of air collide with dust. particles
→ Similarly, smoke also move randomly because the random moving particle again and again.

Diffusion

→ The process of mixing of two substances due to Brownian, Brownian motion of particles is called Diffusion.
→ As temp. Increases, Brownian motion increase and diffusion become fast.
→ Diffusion takes place from higher concentration to lower concentration.
→ It is a natural process.
→ It takes place in solid, liquid and gas.

Three states of matter

There are three states of matter

(i) Solid

→ Solids have fixed volume and shape.
→ In solid, particle is closely packed and they have very less spacing between them.
→ In solid, particles only vibrate at their position and they have less kinetic energy.
→ The force of attraction between the particles of solid is very strong.
Ex: - Stone, wood, brick, ice, sugar, coal etc.

(ii) Liquid

→ Liquid have fixed volume but indefinite shape.
→ In liquid there is a weaker force of attraction and more spacing between the particles.
→ In liquid, particle can move around and have high kinetic energy.
Ex:-Milk, water, petrol, alcohol.

(iii) Gas

→ Gases have indefinite shape and volume.
→ Particles of gases have very large spacing and very weak attraction between them.
→ Particle of gases move around easily and have very high kinetic energy.

CHANGE OF STATE OF MATTER

→ Matter can be changed from one state to another state.
i.e - a solid can be changed to liquid and liquid can be changed into gas.


The change of state of matter mainly depend upon two factor

A.TEMPERATURE

→ By increasing the temp, a solid can be converted into gaseous state.
→ By decreasing temp, a gas can be converted into liquid state and liquid can be converted into solid state.

(a) Solid to liquid

→ The process in which a solid substance changes into a liquid on heating is called melting (fusion).
 Ex:-Ice melt to become water.
→ The temperature at which a solid substance melts and changes into a liquid at atmospheric pressure is called
melting point of the substance.
 Ex-ice melt at temp 0 degree celsius to become water so melting point of is 0 degree celsius.
→ The melting point of a solid is a measure of the force of attraction between its particles.
→ When a solid is heated sufficiently, it changes physical state and become a liquid.

(b)  Liquid to gas

→ The process in which a liquid substance changes into rapidly on heating substance changes into a gas rapidly
on heating is called boiling.
→ The temperature at which a liquid boils and changes rapidly on heating is called boiling point.
 Ex:-When water is heated at 100 degree celsius it boils to from gas called steam .So the point of water is 100 degree celsius.
→ The boiling point of a liquid measures the force of attraction between its particles.

(c) Gas to liquid

→ The process of changing a gas to liquid by steam changes into water on cooling called condensation of  steam.

(d) Liquid to solid

→ The process of changing a liquid into a solid by cooling is called freezing.
 Ex:-When water is cooled, it gets converted into solid called ice. This is called freezing of water.

LATENT HEAT

 Normally, when heat is given to substance, then its temp rises.
  This however, is not so when a change of state of a substance a takes place .Because when heat is given to change the physical state of a substance.
There is no rise in temp of the substance. The heat we supply is used up in overcoming the force of attraction between the particles of a substance during state change.

DEFINATION

The heat energy which has to be supplied to change the state of a substance is called latent heat.

The latent heat is of two types

(i) Latent heat of fusion ( solid to liquid )

The latent heat of fusion (or melting) of a solid is the quantity of heat in joules required to convert 1k.g of solid to
liquid, without any change in temp.
Ex:-Latent heat of fusion of ice is
3.34×10^5 J/kg.

(ii) Latent heat of vaporization ( liquid to gas )

  The latent heat of vaporization of a liquid is quantity of heat in joule required to convert 1kg of liquid to gas without any change in temperature.
Ex - The latent heat of vaporization of water is 22.5×10^5 J/kg.

SUBLIMATION

The changing of a solid directly into vapour on heating and of vapours into solid on cooling is
known as sublimation.
 Solid vapour

B. PRESSURE

→ The physical state of matter can also be changed by changing the pressure.
→ Gases can be liquefied by applying high pressure and lowering the temp.
→ There is a lot of space between the particles of a gas. When pressure is applied the particles get so close together that they attracting each other to from a liquid.

 Ex:-Ammonia gas can be liquefied by applying high pressure and lowering temp.

EVAPORATION

→ When liquid is left exposed to air, its volume decrease gradually. This is due to evaporation.
Definition:-The process of liquid changing into vapour even below its boiling point is known as evaporation.
→ Evaporation of liquid can take place even at room temp.
→ Whatever be the temp at which evaporation take place the latent heat of vaporization must be supplied
whenever a liquid change into vapour.
Ex:-
1. Wet clothes dry due to evaporation of water.
2. Common salt is also recovered from sea water by the process of evaporation.

FACTORS AFFECTING EVAPORATION

1. Temperature:- The rate of evaporation increase on increasing the temp. of the liquid .

2. Surface area of liquid:-The rate of evaporation increases on increasing the surface area of liquid .

3. Humidity of Air:-When humidity of air is low, then the rate of evaporation is high and when humidity of air is high the rate of evaporation is low.

4. Wind speed:-The rate of evaporation of a liquid increase with increasing wind speed.

COOLING CAUSED BY EVAPORATION

The cooling caused by evaporation is based on the fact that when a liquid evaporates ,it takes the latent heat of anything it touches, by loosing heat anything get cooled.

Ex:-1. During summer days, water is usually kept in an earthen pot to keep it cool.
 The earthen pot has a large no. of extremely small pores in its walls. Some of water continuously keeps seeping though these pores to the outside of the pot. This water evaporates continuously and takes the latent heat required for vaporization from the earthen pot and the remaining water loses heat and gets cooled.

Ex:-2 If we put a little of spirit at the back of our hand and wave it around the spirit evaporates rapidly and our hand
feels very cold.

Ex:-3 Perspiration (or sweating) is our body’s method of maintaining a content temp.

PLASMA AND BOSE-EINSTEIN CONDENSATE

PLASMA-

→ Plasma is a mixture of free electrons and ions.
→ It occurs naturally in the stars.
→ The sun and other stars glow because of the presence of plasma makes a fluorescent tube (or neon sign bulb)to glow.

BOSE EINSTEIN CONDENSATE-

→ It can be obtain by cooling a gas of extremely low density to super low temp.