NCERT Solution for Class 10 Science Chapter 2 Acids Bases and Salts Text Book Solution and Important QUeston MCQs and Notes Free Download PDF
Acids | Class 10 Science Chapter 2
Acids is defined as the one which produces hydrogen ions in water. For Example, Sulphuric Acid, Hydrochloric Acid etc.
Arrhenius Concept: According to his way of judging substances, he classified the acids and bases as given below:
Acids are those that when dissolved in water, give hydrogen ion or we can write hydronium ion (H3O+)
This hydronium ion is formed due to the combination of hydrogen ion produced by acid with water molecule.
Classification Of Acids:
we have different classification based on different factors so let’s sum up and make ourselves familiar with it.
1. Depending upon source from which they are obtained
- Organic acids
- Inorganic acids
Organic Acids are obtained from plants and animals or we can say they are present in organic matter.
Example: in tomato, oxalic acid is present , in apple, malic acid and in lemon, we have citric acid and so many other acids are present in different organic substances.
Inorganic Acids are those that are obtained from minerals present in earth. These are quite reactive in nature. Example we have are : nitric acid, sulphuric acid, etc.
2. Classification of acids on the basis of strength
If we talk about strength, it means the amount of hydrogen ions given out when acid is dissolved in water.
On the basis of this we have two categories of acids –
- Strong acids
- Weak acids
Strong Acid is the acid that completely dissociates into hydrogen ion. These acids totally dissociate and leave no dissociated molecule of acid.
Example: Hydrochloric acid, sulphuric acid, etc. Weak Acid is the acid that partially dissociates into hydrogen ions. There actually
exists the equilibrium between dissociated ions and undissociated molecules of acids .
Example: Carbonic acid.
3. Classification of acids on the basis of water content
- Dilute acid
- Concentrated acid
- Dilute Acid is the acid that has more amount of water in it and less salt content.
- They are not quite strong.
Concentrated Acid is that which has less amount of water in it and more amount of salt content.
We can dilute the concentrated acid but need to take certain precautions as follows-
One can dilute concentrated acid by adding concentrated acid slowly in water with continuous stirring. By doing so, the heat released is comparatively less and is constantly absorbed by water. So, it prevents the reaction from becoming violent.
Bases | Class 10 Science Chapter 2
If we talk about bases, according to Arrhenius, they are those that when dissolved in water give hydroxide ion (OH–)
Calcium hydroxide Ca(OH)2
Magnesium hydroxide Mg(OH)2
Classification of bases:
1. Classification of bases on the basis of their solubility in water
The bases that are soluble in water are called alkalis.
Note : it is interesting to note that all bases are not alkalis but all alkalis are bases.
2. Classification on the basis of strength
- strong bases
- weak bases
Strong Bases: That completely dissociates in water to give hydroxide ions. These bases totally dissociates and leave no dissociated molecule of base.
Example: Hydroxides of all reactive metals
Weak Bases: That do not completely dissociates in water to give hydroxide ions.
There actually exists the equilibrium between dissociated ions and undissociated molecules of bases.
Example: Calcium hydroxide etc.
Class 10 Science Chapters 2 Acids Bases and Salts
Physical Properties Of Acids And Bases
Some physical properties of acids are as follows –
- They are sour.
- They turn blue litmus red.
- They are corrosive in nature
Some physical properties of bases are as follows –
- They are bitter.
- They turn red litmus blue.
- They are soapy in nature
Chemical Properties of acids and bases
Chemical properties of acids
1. Action with Indicators: when treated with litmus, they turned blue litmus red.
2.Reaction with Metals: They react with acid to form metal salt and hydrogen gas
Acid +metal →metal salt + hydrogen gas
Example : HCl+Zn→ZnCl2+H2
3. Action with metal carbonate and metal bicarbonate
Whenever acids react with metal carbonate or metal bicarbonate, they form respective salts, water and carbon dioxide gas is released.
Example : acid + metal carbonate →metal salt + water + carbon dioxide gas
i.e. HCl +Na2CO3→NaCl +H2O+CO2
4. Reaction with Bases:
Acids react with bases to form salt and water.
i.e. Acid + base →salt and water
This reaction is regarded as neutralization reaction as salt formed is neither acidic nor basic its neutral
5. All acids act as electrolytes in aqueous states
In aqueous state when current is passed they dissociate into ions . Chemical properties of bases
1.Action with Indicators: They turn red litmus blue
2. Reaction with Metals: They react with base to form oxy salt and hydrogen gas is released.
3. Action with ammonium salts
4. Reaction with Acids:
Acid react with acids to form salt and water
Acid + base →salt and water
This reaction is regarded as neutralization reaction as salt formed is neither acidic nor basic its neutral
5. All bases act as electrolyte in aqueous states i.e. NaOH –> Na+ +OH–
6. Salts are formed when acid and base react with each other.
i.e. acid + base→salt + water
The salts are formed as a result of neutralization reaction as both acid and base neutralize each others effect.
The Nature of Salts Can Be- Class 10 Science Chapter 2
- Acidic Salts
- Basic Salts
- Neutral Salts
It is formed when strong acid react with weak base.
As the acid is strong, therefore, strong character is retained in the salt that is why it comes out to be acidic
Example : HCl+Ca(OH)2 → CaCl2+H2O
It is Formed When Strong Base Reacts With weak acid
Example : NaOH+CH3COOH → CH3COONa+H2O
It is Formed When Weak Or Strong Acid And Base React With Each other. They Cancel Each Other’s Effect And Can Form Neutral Salt
Example : HCl+NaOH→NaCl+H2O
- Ph and its biological importance, indicators Strength of acid and base is expressed in terms of pH
- It is the Logarithm of Reciprocal of Hydrogen ion Concentration.
- i.e.: pH =-LOG(H+)
- The ph of any substance can be detected by using ph paper or ph scale.
- pH scale consist of scale ranging from 0 to 14 .
- pH ranging from 0 to 7 are acids
- pH ranging from 7 to 14 are bases
- And 7 is neutral
For Measuring, We Have Ph Scale Given By: Observations Made On The Bases Of Ph Values Ph Range Indicate the strength of acids and bases as given below :
|More Than 4:||Weak Acid|
|More Than 12:||Strongly Base|
Effect of ph on dilution:
In Case Of Acids On Dilution:Ph Increases as acidic strength decreases
In Case Of Bases On Dilution: Ph Decreases as basic strength decreases
Importance of Ph | Class 10 Science Chapter 2
- Biological Importance: Our Body Works Within 7-7.8 Ph. The Ph Of Acid Rain Is Below 5.6 And This Water Affects Aquatic Life.
- Agriculture: Plants Also Specific Range Of Ph For Survival In Order To Grow Crops
- In Dairies: Ph Value Of Milk Is Adjusted About 6.6. If Ph Falls Below 6.6 It Turns Sour.
- In Tooth Decay: Tooth Decay Starts When Ph Of Mouth Falls Below 5.5. At That Ph Acid Reacts With Calcium Phosphate Of Tooth Enamel And Cause Its Corrosion. When We Eat Some Sugary Substance The Acids Production Is Stimulated That Corrode Enamel.
Indicators: Are the substances that bring about change in themselves when some acid or base is added to Natural and artificial indicators
Natural indicators: Litmus (it is extracted from lichens) original color of litmus is purple but in lab it is used as red and blue litmus.
- Effect of Acid: Turns blue litmus red
- Effect on Base: Turns red litmus blue
- Artificial Indicators: Phenolphthalein, methyl orange
- Effect on phenolphthalein-original colour is colourless
- Acid: Remain colourless
- Base: Turns pink
- Effect on methyl orange: original colour (orange)
- Acid: from orange to red
- Base: from orange to yellow
- We have olfactory indicators as well that bring about a change in smell when any substance is added to it.
Like Onion Extract And Vanilla Extract
- Effect Of Acid On Vanilla Extract: same smell
- Effect Of Base On Vanilla Extract: smell changes
- Effect Of Acid On Onion Extract: same smell
- Effect Of Base On Onion Extract: smell changes
Class 10 Science Chapter 2 Acids Bases and Salts Related FAQ
Which gas is usually liberated when an acid reacts with a metal? Illustrate with an example. How will you test for the presence of this gas?
Solution: When an acid reacts with any metal, salt and hydrogen gas are formed.u003cbr/u003eMetal + Acid → Salt + Hydrogen gas
Metal compound A reacts with dilute hydrochloric acid to produce effervescence. The gas evolvedu003cbr/u003eextinguishes a burning candle. Write a balanced chemical equation for the reaction if one of the compounds formed is calcium chloride.
Solution: As metal compound released is Calcium Chloride the gas evolved here is COu003csubu003e2u003c/subu003e. Hence metal A should be Calcium Carbonate. Hence the reaction between Calcium Carbonate and HCl is.u003cbr/u003eCaCOu003csubu003e3u003c/subu003e (s) + 2HCl (Aq) → CaClu003csubu003e2u003c/subu003e( Aq) + COu003csubu003e2u003c/subu003e (g) + Hu003csubu003e2u003c/subu003eO (l)
What is an acid?
Acids are sour in taste, turn blue litmus red, and dissolve in water to release H+ ions.u003cbr/u003eExample: Sulphuric acid (H2SO4), Acetic Acid (CH3COOH), Nitric Acid (HNO3), etc.
Properties of Acids
Acids have a sour taste.
Turns blue litmus red.
Acid solution conducts electricity.
Release H+ ions in an aqueous solution.
Types of Acids
Natural Acidsu003cbr/u003eMineral Acids
What are Indicators?
Indicators are substances which indicate the acidic or basic nature of the solution by the colour change.
What are bases and alkalies?
Solution. : Bases are bitter in taste, have soapy touch, turn red litmus blue and give hydroxide ions (OH–) in aqueous.u003cbr/u003eExamples: Sodium hydroxide (caustic soda) – NaOHu003cbr/u003eCalcium hydroxide – Ca(OH)2u003cbr/u003ePotassium hydroxide (caustic potash) – (KOH)
Properties of Bases
Have a bitter taste.u003cbr/u003eSoapy to touch.u003cbr/u003eTurns red litmus blue.u003cbr/u003eConducts electricity in solution.u003cbr/u003eRelease OH– ions in Aqueous Solution
pH of a given solution is the negative logarithm to the base 10 of the hydrogen ion concentration, [H+] expressed in g ions/lit or moles/lit. Thusu003cbr/u003epH=- log[H+]
What are the practical applications of neutralisation reactions?
Being alkaline in nature, cold milk is used to neutralise the acidity produced by HCl present in the gastric juice in the stomach.
Astronauts in spaceships use this reaction to neutralise the dangerous levels of CO2.
Farmers add slaked lime (calcium hydroxide) to reduce the acidity of the soil.
The sting of ants and bees contains formic acid. This can be neutralised by rubbing soap, which contains free sodium hydroxide.
Persons suffering from acidity are given antacid tablets, containing magnesium hydroxide which neutralises excess HCl produced, in the stomach. Alternately, they are advised to sip cold milk, which neutralises HCl.
Why the salts solutions of strong acid and strong alkali are neutral?
Let us take the example of potassium sulphate, which is a salt of strong acid [sulphuric acid] and strong base [potassium hydroxide solution] .u003cbr/u003eFrom the above equation, it is clear that water is always feebly ionised and hence the solution of potassium sulphate is neutral in nature.
A salt formed by incomplete neutralization of an acid by a base
When aqueous solutions of hydrochloric acid and sodium hydroxide are mixed in the proper proportion, a reaction takes place to form sodium chloride and water.
HCl(aq) + NaOH(aqr) ↔ NaCl(aq) + H2O(l)
You are given three test tubes. The three test tubes contain distilled water, acidic solution and the basic solution respectively. There is only red litmus paper available in order to identify what is there in each test tube. How will you find out what is in each of the test tubes?
Solution: We can identify the content in each of the test tubes using red litmus paper. This can be done by noticing the colour change of the red litmus paper.
* If the red litmus paper changes to blue colour the solution is a basic solution.
* If the red litmus paper experience no change in acidic solution.
* If the red litmus paper changes to purple colour the solution is distilled water.
Why should curd and sour substances not be kept in brass and copper vessels?
Solution: Curd and sour food substances contain acids; these acidic substances combine with metal. This reaction turns food to poison which damage people’s health.