NCERT Solutions for Class 10 Chapter 2 Acids, bases and salts with questions and answers
NCERT Solutions for Class 10 Chapter 2 Acids, bases and salts with questions and answers help students to get high marks in exams. NCERT Class 10 textbooks solution also available here. NCERT Class 10 Science Solutions also helps to make your study more perfect.
In this lesson we discussed acid bases, salts, indicators; different type of acids like mineral acids, organic acids, strong acids, weak acids, concentrated acids and dilute acids; acid base indicators like Litmus, methyl orange, phenolphthalein; properties of acids and their uses semicolon properties of bases and their uses; what is pH; pH of different solution; properties and uses of some salts like common salt washing soda, bleaching powder ,plaster of Paris.
NCERT Solutions for Class 10 Chapter 2 Acids, bases and salts
Exercises solution
Question 1:
A solution turns red litmus blue, its pH is likely to be
(a) 1 (b) 4 (c) 5 (d) 10
Answer 1: (d)
Bases turn red litmus blue and acids turn blue litmus red. The pH value of bases lies between 7 to 14. So the pH value 10 shows basic nature.
Question 2:
A solution reacts with crushed egg-shells to give a gas that turns lime-water milky. The
solution contains
(a) NaCl (b) HCl (c) LiCl (d) KCl
Answer 2:
(b) The solution contains HCl.
Carbon dioxide turns limewater milky. This carbon dioxide is produced when acid reacts with egg shells. So the solution must be acidic in nature. Hence the solution is hydrochloric acid.
Question 3:
10 mL of a solution of NaOH is found to be completely neutralised by 8 mL of a given
solution of HCl. If we take 20 mL of the same solution of NaOH, the amount of HCl
solution (the same solution as before) required to neutralise it will be
(a) 4 mL (b) 8mL (c) 12 mL (d) 16 mL
Answer 3:
(d) 16 mL of HCl solution will be required.
Question 4:
Which one of the following types of medicines is used for treating indigestion?
(a) Antibiotic
(b) Analgesic
(c) Antacid
(d) Antiseptic
Answer 4:
(c) Antacid is used for treating indigestion.
Question 5:
Write word equations and then balanced equations for the reaction taking
place when −
(a) dilute sulphuric acid reacts with zinc granules.
(b) dilute hydrochloric acid reacts with magnesium ribbon.
(c) dilute sulphuric acid reacts with aluminium powder.
(d) dilute hydrochloric acid reacts with iron filings.
Answer 5:
(a) Sulphuric acid + Zinc → Zinc sulphate + Hydrogen
H2SO4 + Zn → ZnSO4 + H2↑
(b) Hydrochloric acid + Magnesium → Magnesium chloride + Hydrogen
2HCl + Mg → MgCl2 + H2↑
(c) Sulphuric acid + Aluminium → Aluminium sulphate + Hydrogen
3H2SO4 + 2Al → Al2(SO4)3 + 3H2↑
(d) Hydrochloric acid + Iron → Ferric chloride + Hydrogen
6HCl + 2Fe → 2FeCl3 + 3H2↑
NCERT Solutions for Class 10 Chapter 2 Acids, bases and salts
Question 6:
Compounds such as alcohols and glucose also contain hydrogen but are not categorized as acids. Describe an activity to prove it.
Answer 6:
Acids are those substances which produce hydronium ions in their aqueous solution. Hence aqueous solution of acids can conduct electricity. But all the hydrogen containing compounds do not produce hydronium ions in their aqueous solution. Hence do not conduct electricity. The compounds such as alcohols and glucose also contain hydrogen but they do not produce hydronium ion in their aqua solution and do not conduct electricity.
Hence they are not categorised as acids.
By the activity below we can prove that alcohols and glucose are not acids in spite of the containing hydrogen.
We take solutions of glucose for alcohols in a beaker. Then 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 volt battery through a switch and a bulb.
Now we switch on the current and the bulb does not glow. This shows that glucose solution (or alcohol solution) does not conduct electricity. Hence they are not considered as acids.
Question 7:
Why does distilled water not conduct electricity, whereas rain water does?
Answer 7:
Since there are no ions present in distilled water hence it does not conduct electricity.
On the other hand rain water contains impurities like acids (carbonic acids etc) in it, that is rain water contains ions. Hence they conduct electricity.
Question 8:
Why do acids not show acidic behaviour in the absence of water?
Answer 8:
Pure acids that means in the absence of water, acids do not contain any hydrogen ions. Hence do not show acidic behaviour.
On the other hand, dilute acids or acids contain water, dissociates to form hydrogen ions and show acidic properties.
Question 9:
Five solutions A, B, C, D and E when tested with universal indicators showed pH as 4, 1, 11, 7 and 9, respectively. Which solution is
(a) neutral?
(b) strongly alkaline?
(c) strongly acidic?
(d) weakly acidic?
(e) weakly alkaline?
Arrange the pH in increasing order of hydrogen-ion concentration.
Answer 9:
(a) Neutral → Solution D with pH 7
(b) Strongly alkaline → Solution C with pH 11
(c) Strongly acidic → Solution B with pH 1
(d) Weakly acidic → Solution A with pH 4
(e) Weakly alkaline → Solution E with pH 9
The pH can be arranged in the increasing order of the concentration of hydrogen ions as:
11 < 9 < 7 < 4 < 1
Question 10:
Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid (HCl) is added to test tube A, while acetic acid (CH3COOH) is added to test tube B. In which test tube will the fizzing occur more vigorously and why?
Answer 10:
The fizzing will occur more vigorously in test tube A, in which hydrochloric acid (HCl) is added.
This is because hydrochloric acid is a stronger acid than acetic acid so reaction will occur more faster in case of hydrochloric acid than acetic acid and therefore produces hydrogen gas at a faster speed due to which fizzing occurs more in case of hydrochloric acid.
Question 11:
Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd? Explain your answer.
Answer 11:
When milk turns into curd, the pH of the solution decreases because when milk turns into curd the solution becomes more acidic. Hence the pH value decreases from 6.
NCERT Solutions for Class 10 Chapter 2 Acids, bases and salts
Question 12:
A milkman adds a very small amount of baking soda to fresh milk.
(a) Why does he shift the pH of the fresh milk from 6 to slightly alkaline?
(b) Why does this milk take a long time to set as curd?
Answer 12:
(a) The milkman shifts the pH of the fresh milk from 6 to slightly alkaline because in
alkaline condition, milk does not set as curd easily due to formation of lactic acid in it.
(b) the slightly alkaline milk takes longer time to set into curd because the lactic acid being formed during curdling has to first neutralize the alkali present in it.
Question 13:
Plaster of Paris should be stored in a moisture-proof container. Explain why?
Answer 13:
Plaster of Paris (POP) should be stored in a moisture-proof container because Plaster of Paris, a powdery mass, absorbs water (moisture) to form a hard solid because of hydration and the solid known as gypsum.
Question 14:
What is a neutralization reaction? Give two examples.
Answer 14:
A reaction in which an acid and base react with each other to give a salt and water and both losses their properties is
termed as a neutralization reaction.
Acid + Base → Salt + Water
For example:
(i) when hydrochloric acid reacts with sodium hydroxide forms salt called sodium chloride and water.
HCl + NaOH → NaCl + H2O
(ii) magnesium Hydroxide reacts with hydrochloric acid to form magnesium chloride and water.
Mg(OH)2 + 2HCl → MgCl2 + 2H2O
Question 15:
Give two important uses of washing soda and baking soda.
Answer 15:
Two important used of washing soda and baking soda are as
follows:
(1) Washing soda:
Washing soda is used as a cleansing agent for domestic purposes like washing clothes
Washing soda is used for removing permanent hardness of water.
(2) Baking soda:
(a) baking soda is used as an antacid in medicine to remove acidity of the stomach
(b) baking soda is used in making baking powder which is used in making cakes,bread etc
NCERT BOOK Intext Questions (page 18):
Question 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 1:
We put the red litmus paper in all the test tubes, one by one. The solution which turns red litmus to blue will be a basic solution. The blue Litmus Paper formed hair can now be used to test acidic solutions.
Now we put the blue Litmus Paper in the remaining two test tubes, one by one. The solution which turns the blue litmus Paper to red will be the acidic solution.
The solution which has no effect on any litmus paper will be a neutral and hence it will be distilled water.
NCERT BOOK Intext Questions (page 21):
Question 1:
Why should curd and sour substances not be kept in brass and copper vessels?
Answer 1:
Curd and sour substances are not kept in brass and copper vessels because curd and other sour substances contain acids. As a results, when they are kept in
brass and copper vessels, the metal reacts with the acid to liberate hydrogen gas
and harmful salts. Therefore, it is not advisable to keep them in these containers.
Metal + Acid → Salt + Hydrogen gas
Question 2:
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?
Answer 2:
When metal reacts with an acid usually forms hydrogen gas.
When zinc reacts with dilute hydrochloric acid forms hydrogen gas along with zinc chloride.
Zn + 2HCl → ZnCl2 + H2↑
Question 3:
Metal compound A reacts with dilute hydrochloric acid to produce effervescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction if one of the compounds formed is calcium chloride.
Answer 3:
Since the produced gas comes out as effervescence and extinguishes a burning candle, so the gas is carbon dioxide and this carbon dioxide is formed when metal compound A reacts with dilute hydrochloric acid. So the metal compound A is a metal carbonate. Since one of the products is calcium chloride then the metal compound is calcium carbonate. So when calcium carbonate reacts with dilute hydrochloric acid forms calcium chloride and carbon dioxide.
πΆππΆπ3 + 2π»πΆπ → πΆππΆl2 + πΆπ2↑+ π»2π
NCERT Solutions for Class 10 Chapter 2 Acids, bases and salts
NCERT BOOK Intext Questions (page 25):
Question 1:
Why do HCl, HNO3, etc., show acidic characters in aqueous solutions while
solutions of compounds like alcohol and glucose do not show acidic character?
Answer 1:
In aqueous solution hydrochloric acid nitric acid dissociates to form hydronium ion ( hydrogen ion combines with water molecule to form hydronium ion H3O+) and shows acidic property.
On the other hand, alcohol and glucose in their aqueous solution do not produce any hydronium ions and do not show acidic property.
The reaction is as follows:
HCl → H+ + Cl
H+ + H2O → H3O+
Question 2:
Why does an aqueous solution of an acid conduct electricity?
Answer 2:
In aqueous solution, acid dissociates to form ions. These ions help to conduct electricity.
Question 3:
Why does dry HCl gas not change the colour of the dry litmus paper?
Answer 3:
Dry hydrochloric acid does not dissociate to form hydrogen ions. Hence do not show acidic nature and since Litmus Paper is also dry so hydrochloric acid does not dissociates to form hydrogen ions and does not change the colour of dry Litmus Paper
Question 4:
While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?
Answer 4:
Dilution of concentrated acid is an exothermic process. Care must be taken while mixing concentrated nitric acid or sulphuric acid with water.
The acid must always be added slowly drop-wise to water with constant stirring. If water is added to a concentrated acid, a large amount of heat is produced at once which may cause splashing of acids and cause accidents.
Question 5:
How is the concentration of hydronium ions (H3O+) affected when a solution of
an acid is diluted?
Answer 5:
In aqueous solution acid dissociates to form hydronium ions. When a solution of an acid is diluted then the volume of the solution increases but the number of hydronium ions still remains the same. As a result, concentration of hydronium ions per unit volume will decrease.
Question 6:
How is the concentration of hydroxide ions (OH-) affected when excess base is
dissolved in a solution of sodium hydroxide?
Answer 6:
Base produces hydroxide ions in aqueous solution. The concentration of hydroxide ions (OH−) would increase when excess base is dissolved in a solution of sodium hydroxide.
NCERT BOOK Intext Questions (page 28):
Question 1:
You have two solutions, A and B. The pH of solution A is 6 and pH of solution
B is 8. Which solution has more hydrogen ion concentration? Which of this is
acidic and which one is basic?
Answer 1:
pH of a neutral solution is 7. When the pH of the solution is less than 7 then the solution is acidic in nature and when more than 7 then the solution is basic in nature. Since solution 'A' has pH less than 7 so it is an acidic solution and pH of solution 'B' is more than 7 so it is a basic solution.
Solution 'A' has more hydrogen ion concentration.
Question 2:
What effect does the concentration of H+
(aq) ions have on the nature of the
solution?
Answer 2:
When the concentration of H+ ion is more than the solution becomes more acidic in nature while when concentration of H+ ions is less than the acidic nature of the solution is decrease
Question 3:
Do basic solutions also have H+
(aq) ions? If yes, then why are these basic?
Answer 3:
Yes, the basic solution also has H+(aq) ions. However, their concentration is less as
compared to the concentration of OH−
ions that make the solution basic in nature.
Question 4:
Under what soil condition do you think a farmer would treat the soil of his fields
with quick lime (calcium oxide) or slaked lime (calcium hydroxide) or chalk
(calcium carbonate)?
Answer 4:
If the soil is acidic in nature then to increase the basicity of soil, the farmer would treat the soil with quicklime or slaked lime or chalk.
NCERT BOOK Intext Questions (page 33):
Question 1:
What is the common name of the compound CaOCl2?
Answer 1:
The common name of the compound CaOCl2 is bleaching powder.
Question 2:
Name the substance which on treatment with chlorine yields bleaching powder.
Answer 2:
Calcium hydroxide [Ca(OH)2], on treatment with chlorine Cl2, yields bleaching powder.
Question 3:
Name the sodium compound which is used for softening hard water.
Answer 3:
Washing soda (Na2CO3.10H2O) is used for softening hard water.
Question 4:
What will happen if a solution of sodium hydrocarbonate is heated? Give the
equation of the reaction involved.
Answer 4:
When a solution of sodium hydrocarbonate is heated, sodium carbonate, carbon dioxide, and water
are formed.
2NaHCO3 → Na2CO3 + H2O + CO2
Question 5:
Write an equation to show the reaction between the Plaster of Paris and water.
Answer 5:
Plaster of Paris on mixing with water, it changes to gypsum which is a hard solid mass.
πΆπππ4.½π»2π +3/2 π»2π → πΆπππ4 . 2 π»2π
NCERT Solutions of Class 10 Science all chapters in PDF
Chapter 2 – Acids, bases and salt
Chapter 4 – Carbon and Its Compounds
Chapter 5 – Periodic Classification Of Elements
Chapter 6 – Life Processes
Chapter 7 – Control and Coordination
Chapter 8 – How do Organisms Reproduce?
Chapter 9 – Heredity and Evolution
Chapter 10 – Light Reflection and Refraction
Chapter 11 – The Human Eye and Colourful World
Chapter 12 – Electricity
Chapter 13 – Magnetic Effects of Electric Current
Chapter 14 – Sources of Energy
Chapter 15 – Our Environment
Chapter 16 – Sustainable Management of Natural Resources
The topics and sub-topics in Chapter 1 Acids, Bases and Salts
2.1 Understanding The Chemical Properties of Acids and Bases
2.1.1 Acids and Bases in the Laboratory
2.1.2 How do Acids and Bases React with Metals?
2.1.3 How do Metal Carbonates and Metal Hydrogen carbonates React with Acids?
2.1.4 How do Acids and Bases React with each other?
2.1.5 Reaction of Metallic Oxides with Acids
2.1.6 Reaction of a Non-metallic Oxide with Base
2.2 What Do All Acids And All Bases Have In Common?
2.2.1 What Happens to an Acid or a Base in a Water Solution?
2.3 How Strong Are Acid Or Base Solutions?
2.3.1 Importance of pH in Everyday Life
2.4 More About Salts
2.4.1 Family of Salts
2.4.2 pH of Salts
2.4.3 Chemicals from Common Salt
2.4.4 Are the Crystals of Salts really Dry?.
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