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
1. Why should curd and sour substances not be kept in brass and copper
vessels?
Answer:
Curd and sour 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.
vessels?
Answer:
Curd and sour 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.
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:
Hydrogen gas is generally liberated when acid reacts with metal.
e.g- H2SO4 + Zn -> ZnSO4+ H2
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:
CaCO3 (s) + 2HCl (Aq) → CaCl2( Aq) + CO2 (g) + H2O (l)
Page no - 25
Illustrate with an example. How will you test for the presence of
this gas?
Answer:
Hydrogen gas is generally liberated when acid reacts with metal.
e.g- H2SO4 + Zn -> ZnSO4+ H2
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:
CaCO3 (s) + 2HCl (Aq) → CaCl2( Aq) + CO2 (g) + H2O (l)
Page no - 25
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:
An acid is a substance which dissociate on dissolving in water to produce hydrogen ions (H+)
An aqueous solution of HCl and HNO3 dissociate to hydrogen ions.
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.
while solutions of compounds like alcohol and glucose do not show acidic
character?
Answer:
An acid is a substance which dissociate on dissolving in water to produce hydrogen ions (H+)
An aqueous solution of HCl and HNO3 dissociate to hydrogen ions.
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.
2. Why does an aqueous solution of an acid conduct electricity?
Answer:
Acids dissociates on dissolving in water to produce charged ions. These ions conduct electricity in aqueous solution of an acid.
Answer:
Acids dissociates on dissolving in water to produce charged ions. These ions conduct electricity in aqueous solution of an acid.
3. Why does dry HCl gas not change the colour of the dry litmus paper?
Answer:
Dry HCl gas not produce hydrogen ion, therefore it's not acidic in nature and not change the color of dry litmus paper.
4. While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?
Answer:
If water is added to concentrated acid, it release huge amount of heat which may result in explosion . Hence it is safe to add acid to water but not water to acid.
5. How is the concentration of hydronium ions (H3O+) affected when a solution of an acid is diluted?
Answer:
When acid is added to water there will be a fixed amount of hydronium present in the fixed volume of solution. If we dilute the solution hydronium ion per volume of solution decrease, this in-turn decreases Hydronium concentration in the solution.
6. How is the concentration of hydroxide ions (OH-) affected when excess base is dissolved in a solution of sodium hydroxide?
Answer:
When base is dissolved in sodium hydroxide solution its hydroxide ions increase but it will reach saturation at some point. After saturation point hydroxide ion concentration is not affected even after adding base further.
Page no - 28
Answer:
Dry HCl gas not produce hydrogen ion, therefore it's not acidic in nature and not change the color of dry litmus paper.
4. While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?
Answer:
If water is added to concentrated acid, it release huge amount of heat which may result in explosion . Hence it is safe to add acid to water but not water to acid.
5. How is the concentration of hydronium ions (H3O+) affected when a solution of an acid is diluted?
Answer:
When acid is added to water there will be a fixed amount of hydronium present in the fixed volume of solution. If we dilute the solution hydronium ion per volume of solution decrease, this in-turn decreases Hydronium concentration in the solution.
6. How is the concentration of hydroxide ions (OH-) affected when excess base is dissolved in a solution of sodium hydroxide?
Answer:
When base is dissolved in sodium hydroxide solution its hydroxide ions increase but it will reach saturation at some point. After saturation point hydroxide ion concentration is not affected even after adding base further.
Page no - 28
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:
Solution A has more hydrogen ion concentration.
Solution A is acidic and solution B is basic in nature.
2. What effect does the concentration of H+(aq) ions have on the nature of the
solution?
Answer:
Increase in concentration of hydrogen ions in solution makes it acidic. On the other hand decrease in concentration of hydrogen ions makes the solution basic.
3. Do basic solutions also have H+(aq) ions? If yes, then why are these basic?
Answer:
Yes basic solution also have hydrogen ions.
The concentration of hydrogen ions in basic solution is less than hydroxide ions concentration. Higher concentration of hydroxide ions make the solution basic.
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:
If the soil is acidic (pH less than 7), then such field should be treated with quick lime or slaked lime to make the field neutral.
Page no - 33
Which of this is acidic and which one is basic?
Answer:
Solution A has more hydrogen ion concentration.
Solution A is acidic and solution B is basic in nature.
2. What effect does the concentration of H+(aq) ions have on the nature of the
solution?
Answer:
Increase in concentration of hydrogen ions in solution makes it acidic. On the other hand decrease in concentration of hydrogen ions makes the solution basic.
3. Do basic solutions also have H+(aq) ions? If yes, then why are these basic?
Answer:
Yes basic solution also have hydrogen ions.
The concentration of hydrogen ions in basic solution is less than hydroxide ions concentration. Higher concentration of hydroxide ions make the solution basic.
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:
If the soil is acidic (pH less than 7), then such field should be treated with quick lime or slaked lime to make the field neutral.
Page no - 33
1. What is the common name of the compound CaOCl2?
Answer:
Common name of CaOCl2 is bleaching powder.
2. Name the substance which on treatment with chlorine yields bleaching
powder.
Answer:
Calcium hydroxide on treatment with chlorine yields bleaching powder.
3. Name the sodium compound which is used for softening hard water.
Answer:
Sodium carbonate is used for softening hard water.
4. What will happen if a solution of sodium hydrocarbonate is heated? Give the equation of the reaction involved.
Answer:
On heating sodium hydrocarbonate, sodium carbonate and carbon dioxide get fromed.
Answer:
Common name of CaOCl2 is bleaching powder.
2. Name the substance which on treatment with chlorine yields bleaching
powder.
Answer:
Calcium hydroxide on treatment with chlorine yields bleaching powder.
3. Name the sodium compound which is used for softening hard water.
Answer:
Sodium carbonate is used for softening hard water.
4. What will happen if a solution of sodium hydrocarbonate is heated? Give the equation of the reaction involved.
Answer:
On heating sodium hydrocarbonate, sodium carbonate and carbon dioxide get fromed.
5. Write an equation to show the reaction between Plaster of Paris and water.
Answer:
The chemical equation for the reaction of Plaster of Paris and water is
CaSO4.1/2H2O + 3/2H2O → CaSO4.2H2O
Answer:
The chemical equation for the reaction of Plaster of Paris and water is
CaSO4.1/2H2O + 3/2H2O → CaSO4.2H2O
EXERCISES
1. A solution turns red litmus blue, its pH is likely to be
(a) 1 (b) 4 (c) 5 (d) 10
Answer: 10
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
(a) 1 (b) 4 (c) 5 (d) 10
Answer: 10
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: HCl
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
HCl solution (the same solution as before) required to neutralise it will be
(a) 4 mL (b) 8 mL (c) 12 mL (d) 16 mL
Answer: 16ml
4. Which one of the following types of medicines is used for treating indigestion?
(a) Antibiotic
(b) Analgesic
(c) Antacid
(d) Antiseptic
Answer: Antacid
5. Write word equations and then balanced equations for the reaction taking
place when –
(a) dilute sulphuric acid reacts with zinc granules.
Answer: H2SO4(aq) + Zn → ZnSO4(aq) + H2(g)
(b) dilute hydrochloric acid reacts with magnesium ribbon.
Answer: 2HCl(aq) + Mg → MgCl2(aq) + H2(g)
(c) dilute sulphuric acid reacts with aluminium powder.
Answer: 3H2SO4(aq) + 2Al(s) → Al2(SO4)3(aq) + 3H2(g)
(d) dilute hydrochloric acid reacts with iron filings.
Answer: 6HCl(aq) + 3Fe(s) → 3FeCl2(aq) + 3H2(g)
6. Compounds such as alcohols and glucose also contain hydrogen but are not
categorised as acids. Describe an Activity to prove it.
Answer:
Compounds like alcohol and glucose contain hydrogen but they do not ionise in the solution to produce H+ ions on passing current through them. So these are not categorised as acid.
Activity-
Procedure
(i) Take solutions of alcohols and glucose.
(ii) Fix two nails on a cork, and place the cork in 100 mL beaker.
(iii) Connect the nails to the two ends of a 6 volt battery through a bulb and a switch.
Observation
(i) Pour alcohol in the beaker and switch on
the current
(ii) The bulb does not glow.
(iii) Repeat the experiment with glucose. The bulb does not glow in this case also.
(iv) This means no ions or H+ ions are present in the solution.
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
HCl solution (the same solution as before) required to neutralise it will be
(a) 4 mL (b) 8 mL (c) 12 mL (d) 16 mL
Answer: 16ml
4. Which one of the following types of medicines is used for treating indigestion?
(a) Antibiotic
(b) Analgesic
(c) Antacid
(d) Antiseptic
Answer: Antacid
5. Write word equations and then balanced equations for the reaction taking
place when –
(a) dilute sulphuric acid reacts with zinc granules.
Answer: H2SO4(aq) + Zn → ZnSO4(aq) + H2(g)
(b) dilute hydrochloric acid reacts with magnesium ribbon.
Answer: 2HCl(aq) + Mg → MgCl2(aq) + H2(g)
(c) dilute sulphuric acid reacts with aluminium powder.
Answer: 3H2SO4(aq) + 2Al(s) → Al2(SO4)3(aq) + 3H2(g)
(d) dilute hydrochloric acid reacts with iron filings.
Answer: 6HCl(aq) + 3Fe(s) → 3FeCl2(aq) + 3H2(g)
6. Compounds such as alcohols and glucose also contain hydrogen but are not
categorised as acids. Describe an Activity to prove it.
Answer:
Compounds like alcohol and glucose contain hydrogen but they do not ionise in the solution to produce H+ ions on passing current through them. So these are not categorised as acid.
Activity-
Procedure
(i) Take solutions of alcohols and glucose.
(ii) Fix two nails on a cork, and place the cork in 100 mL beaker.
(iii) Connect the nails to the two ends of a 6 volt battery through a bulb and a switch.
Observation
(i) Pour alcohol in the beaker and switch on
the current
(ii) The bulb does not glow.
(iii) Repeat the experiment with glucose. The bulb does not glow in this case also.
(iv) This means no ions or H+ ions are present in the solution.
7. Why does distilled water not conduct electricity, whereas rain water does?
Answer:
Distilled water not contain any ionic species, so it doesn't conduct electricity.
Whereas when rain water comes to the earth it dissolves an acidic gas (CO2) from air and form carbonic acid, which produce ions to rain water.
Due to presence of ions in rain water it conduct electricity.
8. Why do acids not show acidic behaviour in the absence of water?
Answer: Acid shows acidic behaviour due to the H+ ion present in it. The acid produce H+ in only in presence of water, therefore in absence of water acid will not show acidic behaviour.
Answer:
Distilled water not contain any ionic species, so it doesn't conduct electricity.
Whereas when rain water comes to the earth it dissolves an acidic gas (CO2) from air and form carbonic acid, which produce ions to rain water.
Due to presence of ions in rain water it conduct electricity.
8. Why do acids not show acidic behaviour in the absence of water?
Answer: Acid shows acidic behaviour due to the H+ ion present in it. The acid produce H+ in only in presence of water, therefore in absence of water acid will not show acidic behaviour.
9. Five solutions A,B,C,D and E when tested with universal indicator showed pH as
4,1,11,7 and 9, respectively. Which solution is
(a) neutral?
Answer: 7
(b) strongly alkaline?
Answer: 11
(c) strongly acidic?
Answer: 1
(d) weakly acidic?
Answer: 4
(e) weakly alkaline?
Answer: 9
Arrange the pH in increasing order of hydrogen-ion concentration.
11<9<7<4<1
4,1,11,7 and 9, respectively. Which solution is
(a) neutral?
Answer: 7
(b) strongly alkaline?
Answer: 11
(c) strongly acidic?
Answer: 1
(d) weakly acidic?
Answer: 4
(e) weakly alkaline?
Answer: 9
Arrange the pH in increasing order of hydrogen-ion concentration.
11<9<7<4<1
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. Amount and concentration taken for both the acids are same. In which test
tube will the fizzing occur more vigorously and why?
Answer: The fizzing is due to hydrogen gas.
The Hydrochloric acid is stronger than acetic acid and contains more amount of hydrogen ions. Hence fizzing will occur more vigorously in test tube A.
acid (HCl) is added to test tube A, while acetic acid (CH3COOH) is added to test
tube B. Amount and concentration taken for both the acids are same. In which test
tube will the fizzing occur more vigorously and why?
Answer: The fizzing is due to hydrogen gas.
The Hydrochloric acid is stronger than acetic acid and contains more amount of hydrogen ions. Hence fizzing will occur more vigorously in test tube A.
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: Lactic acid get formed when milk changes into curd, which lowers the pH value of milk.
curd? Explain your answer.
Answer: Lactic acid get formed when milk changes into curd, which lowers the pH value of milk.
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?
Answer: Milk is made slightly alkaline so that it may not get sour easily due to formation on lactic acid in it.
(b) Why does this milk take a long time to set as curd?
Answer: To form lactic acid, milk has to first neutralise the alkali present in it. So the alkaline milk take longer time to set as curd than usual.
13. Plaster of Paris should be stored in a moisture-proof container. Explain why?
Answer: Plaster of Paris should be stored in a moisture-proof container because plaster of paris reacts with water to form Gypsum ( hard substance).
(a) Why does he shift the pH of the fresh milk from 6 to slightly alkaline?
Answer: Milk is made slightly alkaline so that it may not get sour easily due to formation on lactic acid in it.
(b) Why does this milk take a long time to set as curd?
Answer: To form lactic acid, milk has to first neutralise the alkali present in it. So the alkaline milk take longer time to set as curd than usual.
13. Plaster of Paris should be stored in a moisture-proof container. Explain why?
Answer: Plaster of Paris should be stored in a moisture-proof container because plaster of paris reacts with water to form Gypsum ( hard substance).
14. What is a neutralisation reaction? Give two examples.
Answer:
A reaction in which acid and base react with each other to form salt and water is known as neutralization reaction.
e.g- HCl + NaOH -> NaCl + H2O
NaOH + H2SO4 -> Na2SO4 + H2O
15. Give two important uses of washing soda and baking soda.
Answer:
Use of washing soda
(i) It used in industries such as paper, soap and glass.
(ii) It used to remove permanent hardness of water.
Answer:
A reaction in which acid and base react with each other to form salt and water is known as neutralization reaction.
e.g- HCl + NaOH -> NaCl + H2O
NaOH + H2SO4 -> Na2SO4 + H2O
15. Give two important uses of washing soda and baking soda.
Answer:
Use of washing soda
(i) It used in industries such as paper, soap and glass.
(ii) It used to remove permanent hardness of water.
Quick revision note of class 10 science
chapter 3 Acids, Bases and Salts
No comments:
Post a Comment
If you have any doubt, let me know ☺️