Acid Bases & Salts Important Questions Class 10 Science with Solutions
Chemistry, with its confusing reactions and complex equations, can often seem tough to Class 10 students. Among the most important chapters in the syllabus are acids, bases, and salts. This chapter is a basis for understanding chemical properties and reactions, and it is essential not only for exams but also for building a strong base in chemistry. To perform well in this subject, it’s essential to practice and revise through aClass 10 Science Chapter 2 Important Questions.
We will help you understand why acids, bases, and salts in Class 10 are important for your preparation, how you can effectively use them to study smarter, and some unique tips to ensure you understand this chapter.
(Most Important Questions of this Chapter from our 📕)
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Chapter 2 Acids Bases and Salts : Important Questions
1. Which of these graphs shows how the pH of milk changes as it forms curd?
Answer: Graph A
Explanation:
During the process of curd formation, milk undergoes fermentation, during which lactic acid bacteria convert lactose into lactic acid. This increases the acidity of the milk, leading to a gradual decrease in pH over time.
2. The following table lists the pH values of some substances.
Solutions
pH
Hydrochloric Acid
1
Milk
6
Pure Water
7
Baking Soda
9
Sodium Hydroxide
14
What would happen to the pH of an acid and a base when each is diluted (pure distilled water is added to it)?
Answer:
When a substance is diluted with pure distilled water:
For an Acid: The pH will increase (become less acidic).
Adding water decreases the concentration of hydrogen ions [H+], reducing acidity and moving the pH closer to 7.
For a Base: The pH will decrease (become less basic).
Adding water decreases the concentration of hydroxide ions [OH−], reducing basicity and moving the pH closer to 7.
However, in both cases, the substance will not become neutral unless diluted extensively.
3. A remarkable property of acids is that they can 'dissolve' metals. When metals are added to an acid, they disintegrate and disappear into the acid.
(a) State one other common observation when metals 'dissolve' in acids. Explain the reason for this observation.
(b) If the acid with the 'dissolved' metal is evaporated, can we get the metal back? Why or why not?
(c) In this question, the word 'dissolve' is used within quotes. This is because it is not actually an example of dissolving.
What is the MAIN difference between a metal 'dissolving' in an acid and sugar dissolving in water?
Answer:
(a) State one other common observation when metals 'dissolve' in acids. Explain the reason for this observation.
Observation: Effervescence (bubbles) is commonly observed when metals 'dissolve' in acids.
Explanation: The effervescence occurs due to the production of hydrogen gas (H2) as a result of the chemical reaction between the metal and the acid. The reaction can be represented as:
Metal+Acid→Salt+Hydrogen
For example:
Zn+2HCl→ZnCl2+H2↑
The bubbles are the visible release of hydrogen gas.
(b) If the acid with the 'dissolved' metal is evaporated, can we get the metal back? Why or why not?
No, the metal cannot be recovered by evaporating the acid.
Reason: When a metal reacts with an acid, it forms a salt and hydrogen gas is released. The metal is chemically transformed into a salt, and the original metal atoms are no longer in their elemental form. Evaporation of the acid will only leave behind the salt but not the original metal.
(c) In this question, the word 'dissolve' is used within quotes. This is because it is not actually an example of dissolving. What is the MAIN difference between a metal 'dissolving' in an acid and sugar dissolving in water?
The main difference is chemical reaction vs physical process:
Metal 'dissolving' in acid: This involves a chemical reaction where the metal reacts with the acid to form a new compound (salt) and releases hydrogen gas. The metal's composition is altered.
Sugar dissolving in water: This is a physical process where sugar molecules disperse in water without undergoing any chemical change. The sugar retains its chemical identity and can be recovered unchanged by evaporation.
4. To prepare a salad dressing, Parag adds a solution of sodium chloride in distilled water to vinegar.
State what change will occur in the following:
(i) the pH of the vinegar
(ii) the acidity of the vinegar
Answer:
When sodium chloride (NaCl) solution is added to vinegar, the following changes occur:
(i) The pH of the vinegar:
There will be no significant change in the pH of the vinegar.
Sodium chloride is a neutral salt that does not affect the concentration of hydrogen ions (H+) in the solution. Hence, the acidity (pH) of the vinegar remains largely unchanged.
(ii) The acidity of the vinegar:
The acidity of the vinegar decreases slightly.
Acidity refers to the concentration of hydrogen ions (H+). When sodium chloride solution is added, it dilutes the vinegar, reducing the relative concentration of hydrogen ions in the solution. This reduces the acidity, even though the pH may not change significantly.
In summary:
The pH remains nearly constant because the dilution effect is minimal and sodium chloride does not react with the acetic acid.
The acidity decreases due to the dilution of the vinegar.
5. Rajesh was given a substance and asked to identify it. He conducted three tests on the substance and recorded the results below.(P) It releases carbon dioxide, water and a sodium salt on heating with water.(Q) It turns universal indicator greenish-blue.(R) It can be prepared from ammonia as a raw material.
5.1 What substance was Rajesh given?
5.2 Give ONE use of the substance based on the properties mentioned in P and Q.
5.3 Rajesh later read that recrystallisation of the sodium salt formed in P gives another basic salt that is used in manufacture of borax.
Identify the sodium salt formed in P.
Answer:
5.1 The substance Rajesh was given is sodium carbonate (Na₂CO₃).
Explanation:
(P): When heated with water, sodium carbonate releases carbon dioxide, water, and a sodium salt. This suggests a reaction where sodium carbonate breaks down or reacts with water.
(Q): It turns universal indicator greenish-blue, indicating the substance is alkaline (basic), which fits sodium carbonate, a base.
(R): Sodium carbonate can be prepared from ammonia as a raw material through the Solvay process, where ammonia is involved in the production of sodium carbonate.
5.2 One use of sodium carbonate (based on its properties in P and Q) is in the manufacture of glass. Sodium carbonate is used to lower the melting point of silica in glass production, and its basic nature (as shown in Q) is useful in many chemical processes.
5.3 The sodium salt formed in P is sodium bicarbonate (NaHCO₃).
Explanation: When sodium carbonate reacts with water and carbon dioxide, sodium bicarbonate is typically formed. Recrystallisation of sodium bicarbonate gives sodium carbonate, and sodium carbonate is involved in the manufacture of borax, which aligns with the statement in R.
6. Dipti has three flasks containing dilute hydrochloric acid, dilute sulphuric acid and dilute sodium hydroxide respectively. The flasks are not labeled and she does not have any pH indicator.
(a) Which of the solutions will she be able to identify just by making mixtures of pairs of the substances.
(b) What observation will help her to make this identification?
Answer:
(a) Which of the solutions will she be able to identify just by making mixtures of pairs of the substances?
Dipti can identify all three solutions (dilute hydrochloric acid, dilute sulfuric acid, and dilute sodium hydroxide) by mixing pairs of the substances. The three substances are:
Dilute hydrochloric acid (HCl)
Dilute sulfuric acid (H₂SO₄)
Dilute sodium hydroxide (NaOH)
By mixing different pairs, she will be able to distinguish them because of the nature of the reactions that occur between acids and bases.
(b) What observation will help her to make this identification?
The observation that will help Dipti identify the solutions is based on the nature of the reactions between acids and bases, which result in neutralization and the formation of salts and water:
Mixing either of the acids (HCl or H₂SO₄) with the sodium hydroxide (NaOH):
Acid + Base → Salt + Water
The reaction between an acid and sodium hydroxide will result in a neutralization reaction, producing heat (exothermic reaction) and water.
This observation (heat and the formation of water) indicates a neutralization reaction, and Dipti can confirm that one of the solutions is sodium hydroxide.
Mixing the two acids (HCl and H₂SO₄):
When the two acids are mixed together, there will be no reaction, as both are acids.
This observation helps identify that the two solutions being mixed are both acidic, and therefore, they must be either dilute hydrochloric acid (HCl) or dilute sulfuric acid (H₂SO₄).
Observing the strength of acidity:
Hydrochloric acid (HCl) is a strong acid and will show a more immediate and noticeable neutralization with sodium hydroxide.
Sulfuric acid (H₂SO₄), though a strong acid, may produce additional reactions due to the presence of sulfate ions, but in dilute form, the reactions with sodium hydroxide will still lead to neutralization.
In summary, the key observations that will help Dipti identify the solutions are:
The formation of heat and water when the base (NaOH) reacts with either acid (HCl or H₂SO₄), indicating a base.
The lack of a reaction when the two acids (HCl and H₂SO₄) are mixed together.
7. pH is measured using a pH meter, which comprises a detecting unit consisting of a pH sensitive glass electrode and an indicating unit which indicates the pH as shown below.
To measure the pH of a solution, the glass electrode is dipped into the solution and the pH is displayed on the screen of the indicating unit. Before measuring the pH of another solution, the glass electrode is rinsed with distilled water and dried carefully with tissue paper.
How is the pH reading of the second solution likely to be affected if the glass electrode is not dried with tissue paper in the following cases?
(i) if the second solution being measured is acidic in nature
(ii) if the second solution being measured is basic in nature
Answer:
If the glass electrode is not dried with tissue paper after rinsing with distilled water before measuring the pH of a second solution, the leftover water can dilute the solution being tested. This dilution can affect the pH reading as follows:
(i) if the second solution being measured is acidic in nature
The presence of distilled water on the glass electrode would dilute the acidic solution. Since dilution of an acid decreases the concentration of hydrogen ions (H+), the pH of the solution would appear higher (less acidic) than its actual value.
(ii) if the second solution being measured is basic in nature
Similarly, the dilution caused by the residual distilled water would decrease the concentration of hydroxide ions (OH−) in the basic solution. As a result, the pH of the solution would appear lower (less basic) than its actual value.
In both cases, drying the electrode with tissue paper ensures accurate pH measurements by preventing unintended dilution.
8. pH is measured on a scale of 0 to 14, with lower values indicating high hydrogen ion concentration (more acidic) and higher values indicating low hydrogen ion concentration (less acidic). A pH of 7 is considered as neutral. Every whole unit in pH represents a ten-fold increase in or decrease in hydrogen ion concentration. What would the hydrogen ion concentration of a solution of pH 4 be compared to a solution of pH 8?
Answer:
The pH scale is logarithmic, meaning that for every whole number change in pH, the hydrogen ion concentration changes by a factor of 10.
If a solution has a pH of 4, it is more acidic, and its hydrogen ion concentration is higher compared to a solution with a pH of 8. To find out how much more concentrated the hydrogen ions are in the pH 4 solution compared to the pH 8 solution, we calculate the difference in pH values.
The difference in pH between 4 and 8 is: 8−4=4
Since each whole pH unit corresponds to a ten-fold change in hydrogen ion concentration, a difference of 4 pH units means the hydrogen ion concentration in the pH 4 solution is 104 (or 10,000) times higher than in the pH 8 solution.
Therefore, the hydrogen ion concentration of the pH 4 solution is 10,000 times higher than the hydrogen ion concentration of the pH 8 solution.
9. Sunita carried out the following reactions in the laboratory:
(i) complete neutralisation of one mole of sodium carbonate with hydrochloric acid
(ii) complete neutralisation of one mole of sodium bicarbonate with hydrochloric acid She found that the amount of carbon dioxide formed in both the reactions was the same.
(a) Is her finding correct? Justify your answer.
(b) How does the amount of salt formed in case (i) compare with the amount of salt formed in case (ii)?
Answer:
(a) Is her finding correct? Justify your answer.
Yes, Sunita's finding is correct. Both reactions (i) and (ii) result in the formation of the same amount of carbon dioxide, because in both reactions, one mole of carbon dioxide is released as a result of the neutralisation process.
Reaction (i): Sodium carbonate reacts with hydrochloric acid as follows: Na2CO3(aq)+2HCl(aq)→2NaCl(aq)+H2O(l)+CO2(g)
In this reaction, 1 mole of sodium carbonate releases 1 mole of carbon dioxide.
Reaction (ii): Sodium bicarbonate reacts with hydrochloric acid as follows: NaHCO3(aq)+HCl(aq)→NaCl(aq)+H2O(l)+CO2(g)
In this reaction, 1 mole of sodium bicarbonate also releases 1 mole of carbon dioxide.
Thus, the amount of carbon dioxide formed in both reactions is indeed the same, as each reaction releases 1 mole of CO₂.
(b) How does the amount of salt formed in case (i) compare with the amount of salt formed in case (ii)?
In reaction (i), 2 moles of sodium chloride (NaCl) are formed per mole of sodium carbonate, because the balanced equation shows 2 moles of NaCl are produced:
Na2CO3(aq)+2HCl(aq)→2NaCl(aq)+H2O(l)+CO2(g)
In reaction (ii), 1 mole of sodium chloride (NaCl) is formed per mole of sodium bicarbonate:
NaHCO3(aq)+HCl(aq)→NaCl(aq)+H2O(l)+CO2(g)
Therefore, the amount of salt formed in case (i) (2 moles of NaCl) is twice the amount of salt formed in case (ii) (1 mole of NaCl).
Introduction to Acids, Bases, and Salts for Class 10
Before going into the benefits of solving Class 10 acids, bases, and salts questions, it’s important to understand why this chapter holds this much importance. Acids, bases, and salts are everyday substances that we see regularly, whether it's acidic lemon juice, basic soap, or table salt. This chapter explains the properties of acids and bases, how they react with each other, and the importance of salts in our daily lives.
The chapter covers key concepts such as the pH scale, neutralisation reactions, common acids and bases, preparation and uses of salts, and much more. Solving acid bases and salts in class 10 extra questions will help students practically apply theoretical knowledge, deepening their conceptual understanding.
Why Focus on Acids, Bases, and Salts in Class 10: Important Questions?
Chemistry, unlike many other subjects, is not just about memorizing formulas; it's about understanding the "why" and "how" behind reactions. Acids, bases, and salts Class 10's important questions require students to apply their knowledge. By solving these questions, students strengthen their grasp of key concepts such as how acids and bases react, how salts are formed, and why the pH scale is important for measuring acidity and alkalinity.
The Class 10 board exams are one of the most important academic stages in a student’s life. Practicing acids, bases, and salts in class 10 important questions is a must. These questions are designed to reflect the kinds of questions that appear in the actual exams. Regular practice will familiarize students with the question patterns and help them manage their time effectively during the exam.
Practicing class 10 acids, bases, and salts important questions helps in developing essential problem-solving skills. Students must know how to analyze reactions, balance chemical equations, and understand the role of various acids, bases, and salts in different chemical processes. This not only prepares them for exams but also for future competitive exams like NEET and JEE.
Students always look for high-scoring topics, and acids, bases, and salts Class 10 important questions are exactly that. These questions often cover topics that frequently appear in exams.
How to Effectively Use Acids, Bases, and Salts: Class 10 Important Questions?
Knowing why these questions are important is just the first step. The next challenge is learning how to use them effectively.
Before you start practicing, it’s important to have all your study material organized. Download the Acid Bases and Salts Class 10: Important Questions PDF that contains all the essential questions in one place.
Don’t rush into solving complex problems. Begin with the basics. Revise key concepts like the properties of acids, bases, and salts; how to use the pH scale; and common reactions between acids and bases. Once you have a good understanding of these, move on to practicing acids, bases, and salts in the important questions in Class 10.
The key to mastering acid bases and salts in class 10 extra questions is consistency, not speed. Instead of trying to solve 50 questions in one go, break them down into smaller batches. Solve five to ten questions daily, and gradually increase the difficulty level as your confidence grows. Make sure to revise and analyze your mistakes regularly to avoid repeating them.
NCERT books are the bible for Class 10 students, and a large chunk of exam questions are derived directly from NCERT concepts. Hence, focusing on acid bases and salts in class 10 extra questions based on NCERT will not only ensure perfect preparation but also improve your understanding of core concepts.
One of the best ways to prepare is by solving past board exam papers. Often, acids, bases, and salts—class 10—important questions are framed similarly to those from previous years. Going through these papers will give you a clear idea of what to expect, how to frame your answers, and the kind of detail required to secure full marks.
Chemistry involves a lot of formulas and reactions, which can be hard to memorize. Create short notes for key formulas, reactions, and definitions related to acids, bases, and salts in Class 10 Important Questions.
Chemistry is a practical subject, and nothing helps you understand concepts better than performing simple experiments at home. For example, you can test the pH of household substances like lemon juice, soap, or vinegar using litmus paper. These small experiments make learning interactive and help beneficially reinforce theoretical concepts.
Acid Bases and Salts Class 10 Extra Questions are a powerful tool in helping students achieve high scores in their chemistry exams. By focusing on practicing these questions, you will not only revise your understanding of important concepts but also improve your problem-solving abilities. Whether it’s through organized study material like an acids, bases, and salts class 10 important questions PDF or practicing class 10 acids, bases, and salts important questions regularly.
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