# NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

Written by Team Trustudies
Updated at 2021-05-07

Acids, bases and salts (chapter 2) class 10 science is a very important chapter of class 10 science. We have made the best quality NCERT solutions for class 10 science chapter 2 Acids, bases and salts which covers each and every aspect of the chapter in very great detail.NCERT solutions for class 10 science chapter 2 Acids, bases and salts all types of questions are covered including intext exercises for a complete understanding of the students. The concepts mentioned in the solutions are precise and to the point for the class 10 CBSE board examination.

The topics included in the chapter 2 class 10 science (Acids, bases and salts) are litmus test of acid and bases, acid and bases in laboratory, the reaction of acids with metal, the reaction of bases with metal, reaction of metal carbonates and metal hydrogen carbonates with acid, reaction of acid and base with each other, reaction of metallic and non-metallic oxides, acid and base in water,strong acid,strong base, importance of Ph values in daily life,salts and its usage

We have also provided a separate NCERT solution for class 10 science chapter 2 Acids, bases and salts intext exercise(Link below).

## NCERT solutions for class 10 Science Chapter 2 Acid Bases And Salts Exercise

Q1 )

A solution turns red litmus blue, its pH is likely to be

• (a) 1
• (b) 4
• (c) 5
• (d) 10

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

Red litmus paper turns blue under the condition of base or alkaline.
pH range of base: above 7
Threfore,
Ans: (d) 10

Q2 )

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

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

Egg shells contains calcium carbonate, which on reaction with HCl liberates CO2 gas which turn lime water to milky.
Therefore, Solution would be
Ans: (b) HCl

Q3 )

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) 8 mL
• (c) 12 mL
• (d) 16 mL

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

Since, 10 ml of NaOH requires 8 ml of HCl for neutralization,20 ml of NaOH will require:
(8 divided by 10)×20 = 16
Therefore,
Ans: (d) 16 ml

Q4 )

Which one of the following types of medicines is used for treating indigestion ?

• (a) Antibiotic
• (b) Analgesic
• (c) Antacid
• (d) Antiseptic

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

(C) Antacid

Antacid are medicines that are used to counteract or neutralize the acid in stomach to relieve from indigestion or heartburn.

Q5 )

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 filing

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

(a) $Zinc+dilutesulphuricacid?Zincsulphate+Hydrogen$

$Zn\left(s\right)+{H}_{2}S{O}_{4}\left(aq\right)$

$?$

$ZnS{O}_{4}\left(aq\right)+{H}_{2}\left(g\right)$

(b) $Magnesiumribbon+dil.Hydrochloricacid?Magnesiumchloride+Hydrogen$

$Mg\left(s\right)+2HCl\left(aq\right)$

$?$

$MgC{l}_{2}+{H}_{2}\left(g\right)$

(c) $Aluminiumpowder+dil.Sulphuricacid?Aluminiumsulphate+Hydrogen$

$2Al\left(s\right)+3{H}_{2}S{O}_{4}\left(aq\right)$

$?$

$A{l}_{2}\left(S{O}_{4}{\right)}_{3}\left(aq\right)+3{H}_{2}\left(g\right)$

(d) $Ironfilings+Dilutehydrochloricacid?Ferricchloride+Hydrogen$

$2Fe\left(s\right)+6HCl\left(aq\right)$

$?$

$2FeC{l}_{3}\left(aq\right)+3{H}_{2}\left(g\right)$

Q6 ) Compounds such as alcohols and glucose also contain hydrogen but are not categorized as acids. Describe an activity to prove it.

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

Alcohols and glucose does not disassociate in water to form hydrogen ions neither do they accept electrons.This is why they are not considered as Acid
An activity to prove it:
The nails are fitted in a cork and are kept in a 100 ml beaker. Then these are connected to the two terminals of a 6 volt battery along with a bulb and a switch. Now some dilute HCl is poured in the beaker and current is allowed to pass through the circuit. The same experiment is carried out using glucose and alcohol solutions separately in place of HCl.

Observations :
The bulb glows in HCl solution only. The reason is that HCl solution dissociates into H+ and Cl– ions which help to conduct electricity while glucose and alcohol solutions do not dissociate into ions and so, do not conduct electricity. That is why we find the bulb glowing in HCl solution only. Conclusions The above activity proves that all acids contain hydrogen but not all compounds containing hydrogen are acids. Due to this reason compounds such as alcohols and glucose although contain hydrogen, but they are not categorized as acids.

Q7 ) Why does distilled water not conduct electricity, whereas rain water does ?

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

For conduction of electricity free ions is needed to carry the charge from one end to another.pH value of water is 7 which states that it is neither acid nor base,it is neutral and does not contain free ion to carry charge.
Distilled water cannot conduct electricity because it does not contain ions while rain water conducts electricity as it contains ions due presence of dissolved salts in it. Distilled water which is a pure form of water, is neither acidic nor basic in nature. So distilled water does not dissociate into ions. Since, conduction of electricity requires free ions so, distilled water does not conduct electricity.Distilled water cannot conduct electricity because it does not contain ions while rain water conducts electricity as it contains ions due presence of dissolved salts in it. Distilled water which is a pure form of water, is neither acidic nor basic in nature. So distilled water does not dissociate into ions. Since, conduction of electricity requires free ions so, distilled water does not conduct electricity.
Rain water being an impure form of water, contains many ionic species. These ions are responsible for electrical conductivity of rain water.

Q8 ) Why do acids not show acidic behaviour in the absence of water ?

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

The main characteristic of acid is that it dissasociate in water to form hydrogen ions or accept electrons. Acids do not show acidic behaviour in the absence of water because the dissociation of hydrogen ions from an acid occurs in the presence of water only.

Q9 )

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
• (b) Strongly alkaline
• (c) Strongly acidic
• (d) Weakly acidic
• (e) Weakly alkaline

Arrange the pH in increasing order of hydrogen ion concentration ?

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

pH scale is a numeric scale which is used to determine whether an element is acid, base or neutral.
pH value less than 7 stands for acid.
pH value 7 stands for neutral.
pH value above 7 stands for base.
Therefore,
(a) Neutral : D solution
(b) Strongly Alkaline : C solution
(c) Strongly Acidic : B solution
(d) Weakly Acidic : A solution
(e) Weakly Alkaline : E solution
Increasing order of hydrogen ion concentration:
11<9<7<4<1
ie, C < E < D < A < B

Q10 )

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 $\left(C{H}_{3}COOH\right)$ is added to test tube B. In which test tube will the fizzing occur more vigorously and why ?

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

Fizzing occurs more vigorously in Test Tube A.

Explanation

Acetic acid (CH3COOH) is a weak acid whereas hydrochloric acid (HCl) is a strong acid. Fizzing occurs in the test tube due to the evolution of hydrogen gas by the action of acid on magnesium ribbon. Since hydrochloric acid is a strong acid a large amount of hydrogen gas is liberated in the test tube A.

Q11 ) Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd? Explain.

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

The pH value of milk will decrease.

Explanation

Fresh milk has a pH 6, during curdling, the lactobacillus keeps growing and it breaks down the lactose (the natural sugar in milk) into lactic acid which acidifies the milk even further. Therefore, the pH of the milk will drop (decrease). As the more acidic the substance the lower the pH.

Q12 )

A milkman adds a very small amount of baking soda to fresh milk.

1. A milkman adds a very small amount of baking soda to fresh milk.
2. Why does this milk take a long time to set as curd ?

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

1. Baking soda is added to Fresh Milk so that it is made slightly alkaline so that it may not get sour easily due to the formation of lactic acid in it.The more acidic the more sourness. Basically baking soda is added to milk to control the sourness of the curd.
2. The fresh milk has to turn acidic to become curd. But when baking soda is added to the milk it turns into alkaline.The alkaline milk takes a longer time to set into curd because the lactic acid being formed has to first neutralise the alkali present in it.

Q13 ) Plaster of Paris should be stored in a moisture proof container. Explain why?

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

Plaster of Paris (pop) should be stored in a moisture proof container because normally pop is in a powder form but the presence of moisture can cause slow setting of plaster of Paris by bringing about its hydration. After setting it turns into a solid structure which is called Gypsum.This will make the plaster of Paris useless.

Q14 ) What is a neutralisation reaction ? Give two examples.

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

The reaction between an acid and a base to form salt and water is called a neutralisation reaction.
In a neutralization reaction between an acid and a base the typical outcome is a salt formed by the positive ion from the base and the negative ion from the acid.

We will look at examples as:
1: Sulphuric Acid and Potassium Hydroxide neutralize each other in the following reaction:
${H}_{2}SO4+2KOH?{K}_{2}S{O}_{4}+2{H}_{2}O$
2: Hydrochloric Acid and Potassium Hydroxide neutralize each other in following reaction:
$HCL+KOH?KCL+{H}_{2}O$

Q15 ) Give two important uses of washing soda and baking soda.

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

Sodium Bicarbonate is known commonly as Baking Soda. There are various uses of baking soda. Some of them are mentioned below:

Uses of Washing soda :
1. Washing soda is used in glass, soap and paper industries
2. It is used for removing permanent hardness of water.
3. Baking soda is used as an antacid in medicines to remove acidity of the stomach.
4. Baking soda is used for making baking powder (used in making cakes, bread, etc.).

## NCERT solutions for class 10 Science Chapter 2 Acid Bases And Salts Intext Exercise

Q1 ) 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?

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

Red litmus paper can be used to identify the content in each test tube. Variation in color of Red Litmus Paper can help in identifying the content.
Red litmus paper has characteristic that it turns blue when is treated with base and turns purple when is treated with a neutral solution. Change of color of the red litmus paper can be observed in the following ways:
(i) If the red litmus paper changes to blue colour the solution is a basic solution.

(ii) If the red litmus paper experiences no change the solution is an acidic solution.

(iii) If the red litmus paper changes to purple colour the solution is distilled water.

Q2 ) Why should curd and sour substances not be kept in brass and copper vessels?

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

Curd and sour substances are acidic in nature i.e, they have acids in them. Brass and copper vessels are metals.
When acids react with metals they form salt and hydrogen gas.
So,when the curd or sour substances are kept in brass and copper vessels ,they react with them and can corrode the vessel and form toxic substances which are very harmful for the human body . That's why the curd and sour substances are not kept in brass or copper vessels.

Q3 ) 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?

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

When an acid reacts with a metal it liberates Hydrogen gas.
Metal + Acid $?$ Salt + Hydrogen gas.

For example:

$Zn\left(s\right)+2HCl\left(aq\right)?ZnC{l}_{2}\left(aq\right)+{H}_{2}\left(g\right)$

To test the presence of hydrogen ${H}_{2}$gas:
Bring a burning splinter near to the mouth of the test tube where ${H}_{2}$ gas is released, the matchstick bums with a pop sound.

Fig. Hydrogen production and testing the presence of it.

Q4 ) Metal compound A reacts with dilute hydrochloric acid to produce effervescence. The gas evolved to extinguish a burning candle. Write a balanced chemical equation for the reaction if one of the compounds formed is calcium chloride.

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

The evolved gas which extinguishes a burning candle is carbon dioxide $C{O}_{2}$.
During chemical reaction,
Since, one of the compounds formed during this reaction is calcium chloride and as carbon dioxide is formed when dilute hydrochloric acid reacts with a metal carbonate producing effervescence , it means the metal compound is calcium carbonate $CaC{O}_{3}$. Hence, the compound A is calcium carbonate.

$CaC{O}_{3}\left(s\right)+2HCl\left(aq\right)$

$?$

$CaC{l}_{2}\left(aq\right)+C{O}_{2}\left(g\right)+{H}_{2}O\left(l\right)$

Q5 ) Why do $HCl,HN{O}_{3}$ etc., show acidic characters in aqueous solutions while solutions of compounds like alcohol and glucose do not show acidic character?

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

The acidic character of a substance is due to the presence of hydrogen ions (H+) ions in its aqueous solution (water solution) and electron acceptance.
$HCl$ and $HN{O}_{3}$shows acidic properties because they produce hydrogen ions when dissolved in water.
The solutions of compounds like alcohol and glucose do not show acidic character because they do not ionise (or dissociate) in water to produce hydrogen ions.

Q6 ) Why does an aqueous solution of an acid conduct electricity?

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

Charged particles are responsible for the conductance of electricity in an acid. Aqueous solutions of acids conduct electricity signifies the existence of ions in these solutions.
Acids dissociate in aqueous solution to form H+ ions. When electricity is passed through an aqueous solution of an acid, the H+ions reach the cathode and each H+ ion picks up one electron from the cathode to form ${H}_{2}$ gas. Because of this reaction, an aqueous solution of acid conducts electricity.

Q7 ) Why does dry $HCl$ gas not change the colour of the dry litmus paper?

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

Dry $HCl$ does not change the colour of dry litmus paper because water is required for the formation of hydrogen ions which is responsible for the change in color of litmus paper. Since there is absence of water in this case, the formation of hydrogen ions won't take place and no colour change would be observed.

Q8 ) While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

While diluting an acid, it is recommended that the acid should be added to water and not water to the acid because if water is added to concentrated acid, it releases a huge amount of heat which may result in explosion and can cause acid burns on face, clothes and body parts. Hence it is safe to add acid to water rather than water to acid.

Q9 ) How is the concentration of hydronium ions ${H}_{3}{O}^{+}$ affected when a solution of an acid is diluted?

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

The concentration of hydronium ions ${H}_{3}{O}^{+}$ decreases when an acid is diluted because, on adding water the ${H}^{+}$ ions of the acid and hydroxyl ions of water react to form water molecules and this in-turn decreases Hydronium concentration in the solution.

Q10 ) How is the concentration of hydroxide ions $O{H}^{–}$ affected when excess base is dissolved in a solution of sodium hydroxide?

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

The concentration of hydroxide ions increases when base is dissolved in Sodium Hydroxide solution till it reaches the saturation at some point. The concentration of hydroxide ions will not get affected if the base is added further after the saturation point is reached.

Q11 ) 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?

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

We can use the rule to find the hydrogen ion concentration which states that, “The pH of any solution is inversely proportional to the hydrogen ion concentration” i.e, the solution that has a lower pH number will have a higher hydrogen ion concentration. Hence, solution A will have a higher hydrogen ion concentration than solution B.
Also the solution with pH below 7 shows acidic behaviour hence solution A is acidic and that for solution B it is greater than 7 so it’s a basic solution.

Q12 ) What effect does the concentration of ${H}^{+}\left(aq\right)$ ions have on the nature of the solution?

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

Hydrogen ion ${H}^{+}\left(aq\right)$ concentration decides the nature of the solution. If Hydrogen ion concentration increases then solution turns acidic and similarly if the solution turns basic, the Hydrogen ion concentration decreases.

Q13 ) Do basic solutions also have ${H}^{+}\left(aq\right)$ ions? If yes, then why are these basic?

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

Yes, basic solutions have ${H}^{+}$ ions. These type of solutions contain more hydroxide ions than ${H}^{+}$ ions. Hence the Hydroxide ions turn solution to basic.

Q14 ) 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)?

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

A farmer should treat the soil of his fields with quick lime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate) if the soil is acidic in nature i.e, pH below 7 which is not suitable for production of crops.

Q15 ) What is the common name of the compound $CaOC{l}_{2}$?

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

Common name of $CaOC{l}_{2}$ is bleaching powder.

Q16 ) Name the substance which on treatment with chlorine yields bleaching powder

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

The substance which on treatment with chlorine yields bleaching powder is Calcium hydroxide.

$Ca\left(OH{\right)}_{2}\left(s\right)+C{l}_{2}\left(g\right)$

$?$

$CaOC{l}_{2}\left(s\right)+{H}_{2}O\left(l\right)$

Q17 ) Name the sodium compound which is used for softening hard water.

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

Sodium carbonate is the compound which is used for softening hard water.

Q18 ) What will happen if a solution of sodium hydrocarbonate is heated? Give the equation of the reaction involved.

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

Heating sodium hydrocarbonate breaks down in sodium carbonate, carbon dioxide gas and water.The reaction is as follows:

Q19 ) Write an equation to show the reaction between the Plaster of Paris and water.

NCERT Solutions for Class 10 Science Chapter 2 Acid Bases And Salts

The chemical equation for the reaction of Plaster of Paris and water is

$CaS{O}_{4}.1/2{H}_{2}O+3/2{H}_{2}O$

$?$

$CaS{O}_{4}.2{H}_{2}O$

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