Class 10 NCERT Solutions Acids Bases and Salts (2)

Scroll down to download pdf file

Class 10 NCERT Solutions Acids Bases and Salts (2)- NCERT Solutions prepared for CBSE students by the best teachers in Delhi.

Class X Chapter 2 – Acids Bases and Salts Science

Page 1 of 14

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: If the colour of red litmus paper gets changed to blue, then it is a base and if there is no colour change, then it is either acidic or neutral. Thus, basic solution can be easily identified.

Let us mark the three test tubes as A, B, and C. A drop of the solution in A is put on the red litmus paper. Same is repeated with solution B and C. If either of them changes colour to blue, then it is basic. Therefore, out of three, one is eliminated. Out of the remaining two, any one can be acidic or neutral. Now a drop of basic solution is mixed with a drop of each of the remaining two solutions separately and then the nature of the drops of the mixtures is checked. If the colour of red litmus turns blue, then the second solution is neutral and if there is no change in colour, then the second solution is acidic. This is because acidic and basic solutions neutralize each other. Hence, we can distinguish between the three types of solutions.

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


Curd and other sour substances contain acids. Therefore, when they are kept in brass and copper vessels, the metal reacts with the acid to liberate hydrogen gas and harmful products, thereby spoiling the food.

Question 2:

Which gas is usually liberated when an acid reacts with a metal? Illustrate with anexample. How will you test for the presence of this gas?


Hydrogen gas is usually liberated when an acid reacts with a metal. Take few pieces of zinc granules and add 5 ml of dilute H2SO4. Shake it and pass the gas produced into a soap solution. The bubbles of the soap solution are formed. These soap bubbles contain hydrogen gas. 

We can test the evolved hydrogen gas by its burning with a pop sound when a candle is brought near the soap bubbles.

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.


Why do HCl, HNO3, etc., show acidic characters in aqueous solutions while solutions of compounds like alcohol and glucose do not show acidic character?


The dissociation of HCl or HNO3 to form hydrogen ions always occurs in the presence of water. Hydrogen ions (H+) combine with H2O to form hydronium ions (H3O+).

The reaction is as follows:

Although aqueous solutions of glucose and alcohol contain hydrogen, these cannot dissociate in water to form hydrogen ions. Hence, they do not show acidic character.

Question 2:

Why does an aqueous solution of an acid conduct electricity?


Acids dissociate in aqueous solutions to form ions. These ions are responsible for conduction of electricity.

Question 3:

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


Colour of the litmus paper is changed by the hydrogen ions. Dry HCl gas does not contain H+ ions. It is only in the aqueous solution that an acid dissociates to give ions. Since in this case, neither HCl is in the aqueous form nor the litmus paper is wet, therefore, the colour of the litmus paper does not change.

Question 4:

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


Since the process of dissolving an acid in water is exothermic, it is always recommended that acid should be added to water. If it is done the other way, then it is possible that because of the large amount of heat generated, the mixture splashes out and causes burns.

Question 5:

How is the concentration of hydronium ions (H3O+) affected when a solution of an acid is diluted?


When an acid is diluted, the concentration of hydronium ions (H3O+) per unit volume decreases. This means that the strength of the acid decreases.

Question 6:

How is the concentration of hydroxide ions (OH−) affected when excess base is dissolved in a solution of sodium hydroxide?


The concentration of hydroxide ions (OH−) would increase when excess base is dissolved in a solution of sodium hydroxide.

Students should free download the NCERT solutions and get better marks in exams. panel of teachers recommend students to practice questions in NCERT books and download NCERT solutions.


Click on the text For more study material for Science please click here - Science

Latest CBSE News

  • There has been news going around that paper has been leaked. This news came to light when Delhi Education Minister tweeted about the images which he got on his whatsapp. He verified the images with the actual accountancy paper and to the shock of everyone the paper matched Set 2 of the accountancy paper. Sisodia immediately got in touch with CBSE to file a complaint. CBSE has come forward and...
  • Important information given in your CBSE Class 10th, 12th Board Examination 2018 Admit Cards: 1) Roll Number:  Roll number is the most critical item on your admit card as it has t be mentioned on all answer sheets thus have to be correct. Please check your roll number, check the format you’re your friends also to ensure no digit is missing and remember your roll number as you will have to mention...
  • The board exam for class 12 Physics is scheduled for 7th March 2018. Physics taken up by science students is a very important subject which is also considered to be very scoring. The students are advised to stick to the syllabus issued by CBSE and follow the guidelines issued by CBSE and NCERT. The students should also refer to the blueprint of physics for class 12 cbse 2018 to prepare for the...
  • As reported earlier NCERT is in the process of revising the NCERT textbooks for all classes. The revised textbooks are expected to be available for the 2018-2019 sessions which is about to start little earlier this year. That’s definitely a good step as NCERT has decided to review the books every year and keep the books updated based on the learning capabilities of students. Due to the regular...
  • The board exams for class 12 and 10 have started from today. Students have been getting best of luck messages from their families and friends. President Ram Nath Kovind has also extended his wishes to the students appearing for these exams by tweeting: "As school board examinations begin all over the country, best wishes to the boys and girls taking the exams as well as to their families. I am...