Class 10 NCERT Acids bases and salts notes ajs, cbse notes class 10 ajslearning, cbse notes ajs, ajs notes class 10, ajslearning, ajs chalo seekhen

NCERT Science - Class 10
Chapter 2 - Acids, Bases and Salts

1. What causes the sour taste in foods?
   A) Sugars
   B) Bases
   C) Acids
   D) Salts
   Answer: C) Acids


2. What is the nature of baking soda solution?
   A) Acidic
   B) Basic
   C) Neutral
   D) Salty
   Answer: B) Basic


3. Which of the following is a natural indicator?
   A) Bromine water
   B) Litmus
   C) Phenolphthalein
   D) Hydrochloric acid
   Answer: B) Litmus


4. What happens to red litmus paper in a base?
   A) It turns blue
   B) It turns red
   C) It remains red
   D) It becomes colorless
   Answer: A) It turns blue


5. Turmeric is an indicator that turns __ in presence of a base.
   A) Red
   B) Blue
   C) Yellow
   D) Reddish-brown
   Answer: D) Reddish-brown


6. Litmus solution is extracted from which plant?
   A) Fern
   B) Lichen
   C) Moss
   D) Algae
   Answer: B) Lichen


7. Which of the following is not an acid-base indicator?
   A) Methyl Orange
   B) Turmeric
   C) Sodium Chloride
   D) Phenolphthalein
   Answer: C) Sodium Chloride


8. What color does phenolphthalein turn in a basic solution?
   A) Red
   B) Pink
   C) Yellow
   D) Colorless
   Answer: B) Pink


9. Which property of acids and bases is used in neutralizing acidity?
   A) Reactivity
   B) Density
   C) Ability to neutralize each other
   D) Viscosity
   Answer: C) Ability to neutralize each other


10. What change occurs when blue litmus is introduced to an acidic solution?
    A) Turns blue
    B) Turns red
    C) No change
    D) Becomes colorless
    Answer: B) Turns red


11. Which acid is commonly found in vinegar?
    A) Hydrochloric Acid
    B) Sulfuric Acid
    C) Nitric Acid
    D) Acetic Acid
    Answer: D) Acetic Acid


12. Which substance is a base?
    A) HCl
    B) NaOH
    C) H2SO4
    D) HNO3
    Answer: B) NaOH


13. Phenolphthalein turns what color in a basic solution?
    A) Red
    B) Blue
    C) Pink
    D) Colorless
    Answer: C) Pink


14. What is the nature of calcium hydroxide?
    A) Acidic
    B) Basic
    C) Neutral
    D) Salty
    Answer: B) Basic


15. Which indicator changes color in the presence of an acid?
    A) Blue Litmus
    B) Red Litmus
    C) Methyl Orange
    D) All of the above
    Answer: D) All of the above


16. Methyl orange turns __ in acidic solutions.
    A) Red
    B) Yellow
    C) Blue
    D) Pink
    Answer: A) Red


17. Which of the following is not an olfactory indicator?
    A) Onion
    B) Vanilla
    C) Clove oil
    D) Phenolphthalein
    Answer: D) Phenolphthalein


18. Acetic acid is the chemical name for ____________.
    A) Vinegar
    B) Baking Soda
    C) Bleach
    D) Lime Juice
    Answer: A) Vinegar


19. Which of these is an example of a strong acid?
    A) HCl
    B) CH₃COOH
    C) NH₄OH
    D) Ca(OH)₂
    Answer: A) HCl


20. Magnesium hydroxide is commonly used as a(n) __.
    A) Acid
    B) Base
    C) Salt
    D) Indicator
    Answer: B) Base

2 Marks Questions

1. Explain why soap solution turns turmeric stain reddish-brown.

Answer: Soap is basic in nature. When it is applied to a turmeric stain, the basic property of the soap reacts with the turmeric causing the color change to reddish-brown.



2. What is the significance of litmus as a natural indicator in acid-base chemistry?

Answer: Litmus is significant because it is a sensitive and easily available indicator for identifying acidic and basic substances. In acid-base chemistry, it visually demonstrates the nature of a substance by changing color: red in acidic and blue in basic environments. This simple yet effective tool is crucial for quick and safe testing.



3. Why is baking soda solution effective against acidity?

Answer: Baking soda solution, being a base, neutralizes the excess stomach acid. This neutralization reaction forms water and a salt, which alleviates the symptoms of acidity and provides relief without causing harm.



4. Describe how synthetic indicators differ from natural indicators.

Answer: Synthetic indicators, like phenolphthalein and methyl orange, are man-made chemicals specifically designed for accurate and clear pH testing. They often provide a more distinct color change at certain pH levels compared to natural indicators like litmus or turmeric, which are derived from natural sources and may have a broader range of color changes.



5. What role do acids and bases play in everyday life? Give two examples.

Answer: Acids and bases are crucial in many everyday processes. For example, acids like vinegar are used in cooking to add flavor, while bases like baking soda are used in baking and as cleaning agents. They are also important in biological processes like digestion, where stomach acid helps in food breakdown.

6. How does red litmus paper react to acidic and basic solutions?

Answer: Red litmus paper turns blue in basic solutions but remains red in acidic solutions.



7. Describe the chemical nature of ammonium hydroxide.

Answer: Ammonium hydroxide (NH₄OH) is a base.



8. What happens to the color of phenolphthalein in an acidic environment?

Answer: In an acidic environment, phenolphthalein remains colorless.



9. Explain the use of methyl orange in an acid-base experiment.

Answer: Methyl orange is used as an indicator in acid-base experiments. It turns red in acidic solutions and yellow in basic solutions.



10. What observation would you expect when sodium hydroxide (NaOH) is tested with blue litmus?

Answer: Blue litmus remains blue or may turn even more intensely blue when tested with sodium hydroxide (NaOH), a base.

11. Name one strong acid and one strong base commonly used in laboratories.

Answer: Hydrochloric acid (HCl) is a strong acid, and sodium hydroxide (NaOH) is a strong base.



12. What is the pH scale used to measure?

Answer: The pH scale is used to measure the acidity or basicity (alkalinity) of a solution.



13. What is the product of the neutralization reaction between hydrochloric acid and sodium hydroxide?

Answer: The product of the neutralization reaction between hydrochloric acid (HCl) and sodium hydroxide (NaOH) is sodium chloride (NaCl) and water (H₂O).



14. Explain the difference between a physical change and a chemical change, providing an example of each.

Answer: A physical change involves a change in the physical properties of a substance without altering its chemical composition (e.g., melting ice). A chemical change, on the other hand, results in the formation of new substances with different chemical properties (e.g., rusting of iron).



15. Describe the properties of acids and give an example of a common acidic substance.

Answer: Acids typically have a sour taste, turn blue litmus paper red, and release hydrogen ions (H+) in aqueous solutions. A common acidic substance is lemon juice, which contains citric acid.

16. What is the law of conservation of mass, and how does it apply to chemical reactions?

Answer: The law of conservation of mass states that in a chemical reaction, the total mass of the reactants equals the total mass of the products. This law ensures that matter is neither created nor destroyed during a chemical reaction.



17. Explain the role of a catalyst in a chemical reaction with an example.

Answer: A catalyst is a substance that speeds up a chemical reaction without being consumed in the process. For example, in the decomposition of hydrogen peroxide (H₂O₂) to water (H₂O) and oxygen (O₂), manganese dioxide (MnO₂) acts as a catalyst.



18. What is the significance of balancing chemical equations, and provide a balanced equation for the combustion of methane (CH₄).

Answer: Balancing chemical equations ensures that the law of conservation of mass is obeyed, meaning that the same number of atoms of each element are present on both sides of the equation. The balanced equation for the combustion of methane is: 

CH₄ + 2O₂ → CO₂ + 2H₂O.



19. Discuss the concept of limiting reactants in chemical reactions, providing an example and calculations.

Answer: Limiting reactants determine the extent of a chemical reaction. For example, in the reaction of 3 moles of hydrogen (H₂) with 1 mole of nitrogen (N₂) to produce ammonia (NH₃), if you have 6 moles of hydrogen and 2 moles of nitrogen, calculate the limiting reactant and the maximum moles of NH₃ formed.

20. Explain the principles of Le Chatelier's principle and how it applies to chemical equilibrium with an example.

Answer: Le Chatelier's principle states that if a system at equilibrium is disturbed by changes in temperature, pressure, or concentration, the system will shift its position to counteract the disturbance. Describe how it applies to the equilibrium of N₂(g) + 3H₂(g) ⇌ 2NH₃(g) when pressure is increased.



21. Discuss the concept of redox reactions, including oxidation and reduction, and provide an example of a redox reaction.

Answer: Redox reactions involve the transfer of electrons between reactants. Describe the oxidation and reduction processes in the reaction between copper (Cu) and silver nitrate (AgNO₃) to form copper nitrate (Cu(NO₃)₂) and silver (Ag).



22. Explain the significance of the pH scale in chemistry and its role in daily life, providing examples.

Answer: The pH scale measures acidity or alkalinity. Discuss the importance of maintaining the pH balance in swimming pools and the human body, and explain how pH levels are adjusted.



23. Describe the process of electrolysis and its applications, providing examples of where it is used in various industries.

Answer: Electrolysis is the process of using an electric current to drive a non-spontaneous chemical reaction. Discuss its applications in industries such as electroplating, water purification, and the production of hydrogen and chlorine gas.

3 Marks Questions

1. Discuss the use of litmus solution as an acid-base indicator with examples.
   • Answer: Litmus solution, extracted from lichen, is a primary acid-base indicator used in labs. It turns red when exposed to acidic substances, such as lemon juice, and blue in basic substances, like soap solution. This makes it an effective and straightforward tool for distinguishing between acids and bases.
2. Explain the reaction that occurs when baking soda is used to treat acidity.
   • Answer: Baking soda (sodium bicarbonate) reacts with stomach acid (hydrochloric acid) to produce sodium chloride (salt), water, and carbon dioxide. This neutralization reaction reduces the acidity in the stomach, providing relief from symptoms like heartburn.
3. Describe the role of natural indicators in identifying acids and bases, using examples.
   • Answer: Natural indicators like turmeric, red cabbage leaves, and litmus change color in the presence of acids or bases. For instance, turmeric turns reddish-brown with bases, while red cabbage juice changes to pink in acidic conditions and green in basic conditions. These indicators are invaluable for safe and simple testing.
4. How does the color change in methyl orange and phenolphthalein indicate the nature of a solution?
• Answer: Methyl orange turns red in acidic solutions and yellow in basic solutions, while phenolphthale in turns colorless in acidic solutions and pink in basic solutions. These color changes provide a clear and precise indication of the solution's pH level, helping to determine whether a solution is acidic or basic.
5. Explain how natural materials can be used as indicators, with examples.
• Answer: Natural materials like red cabbage leaves, turmeric, and petals of certain flowers can act as indicators due to their pigment's reaction to pH levels. For example, red cabbage juice changes color depending on the pH level: pink/red in acidic solutions, and green/blue in basic solutions. Similarly, turmeric turns reddish-brown in the presence of a base.
6. Discuss the role of olfactory indicators in acid-base chemistry with examples.
   • Answer: Olfactory indicators, like onion, vanilla, and clove oil, change their odor in the presence of acids or bases. For example, onion smell diminishes in basic conditions, making it a useful tool for detecting bases without visual indicators.
7. How do acids and bases react differently with phenolphthalein?
   • Answer: Phenolphthalein remains colorless in acidic solutions but turns pink in basic solutions, indicating the presence of a base.
8. Explain the importance of conducting acid-base experiments with multiple indicators.
   • Answer: Using multiple indicators, like litmus, phenolphthalein, and methyl orange, provides a broader range of detection and more accurate identification of substances as acids or bases, as different indicators react differently to varying pH levels.
9. Describe the reaction of sulfuric acid (H2SO4) with blue and red litmus paper. Explain how a base reacts with methyl orange indicator.
   • Answer: Sulfuric acid, being an acid, will turn blue litmus paper red and have no effect on the color of red litmus paper. A base reacts with methyl orange by turning it yellow, indicating its basic nature.

True/False Statements

1. Bases taste sour and acids taste bitter.
   • Answer: False. 
   • Correct Statement: Acids taste sour and bases taste bitter.
2. Soap is acidic in nature.
   • Answer: False. 
   • Correct Statement: Soap is basic in nature.
3. Phenolphthalein turns blue in an acidic solution.
   • Answer: False. 
   • Correct Statement: Phenolphthalein is colorless in an acidic solution and turns pink in a basic solution.
4. Turmeric is a synthetic indicator.
   • Answer: False. 
   • Correct Statement: Turmeric is a natural indicator.
5. Litmus is a dye extracted from a type of animal.
• Answer: False. 
• Correct Statement: Litmus is a dye extracted from lichen, a plant.
6. Dilute sulfuric acid is used to react with zinc granules.
   • Answer: True
   • Correct Statement: Dilute sulfuric acid is used in the experiment.
7. Bubbles are formed in the soap solution because it is flammable.
   • Answer: False
   • Correct Statement: Bubbles are formed due to the gas being evolved during the reaction.
8. The reaction of a metal with an acid results in the formation of a compound called a salt and oxygen gas.
   • Answer: False
   • Correct Statement: The reaction forms hydrogen gas, not oxygen.
9. Activity 2.3 involves repeating the experiment with various acids, and the observations are always the same.
   • Answer: False
   • Correct Statement: The observations may differ with different acids.
10. The equation for the reaction of a metal with an acid is always the same, regardless of the metal or the type of acid used.
    • Answer: True
    • Correct Statement: The reaction equation is consistent for all metals and acids.

Fill in the Blanks

1. Acids turn blue litmus paper to _________.
   • Answer: red
2. Baking soda is a _________ substance used to treat _________.
   • Answer: basic, acidity
3. _________ changes its color to pink in a basic solution.
   • Answer: Phenolphthalein
4. Turmeric turns _________ when it comes in contact with a basic substance.
   • Answer: reddish-brown
5. Litmus solution, when neutral, is _________ in color.
   • Answer: purple
6. In Activity 2.3, the gas evolved during the reaction is passed through _________ solution to observe bubbles.
   • Answer: soap
7. The metal in the reaction with acids displaces _________ atoms from the acids.
   • Answer: hydrogen
8. The summary equation for the reaction of a metal with an acid is: Acid + Metal → _________ + Hydrogen gas.
   • Answer: Salt
9. Activity 2.4 involves the reaction of zinc with _________.
   • Answer: sodium hydroxide
10. Metal carbonates and hydrogen-carbonates react with acids to produce a corresponding salt, carbon dioxide, and _________.
    • Answer: water

5 Marks Questions with Answers

1. Discuss the procedure and importance of using cloth strips soaked in onion juice as an olfactory indicator in acid-base experiments.
   • Answer: The procedure involves soaking cloth strips in onion juice and testing them with acids and bases. The importance lies in the fact that onion juice changes odor in the presence of these substances, providing a non-visual method to detect acids and bases. This is particularly useful in scenarios where color indicators might not be as effective or in educational settings to demonstrate the diversity of chemical indicators.
     
     
2. Explain the chemical reactions of hydrochloric acid (HCl) with different indicators.
   • Answer: When hydrochloric acid is tested with different indicators, it turns blue litmus red (indicating its acidic nature), has no effect on red litmus, turns phenolphthalein colorless, and turns methyl orange red. These reactions help in confirming the acidic nature of HCl.
     
     
3. Describe the significance of using natural indicators like turmeric and litmus in laboratory settings for testing acids and bases.
   • Answer: Natural indicators like turmeric and litmus are significant due to their availability, ease of use, and the clear visual cues they provide when testing substances. Turmeric changes color in the presence of bases, while litmus changes color depending on whether the substance is acidic or basic. Their use in laboratories is crucial for quick and safe identification of chemical nature, especially in educational and preliminary testing scenarios.
     
     
4. Compare and contrast the reaction of acetic acid (CH₃COOH) and sodium hydroxide (NaOH) with litmus paper.
   • Answer: Acetic acid, being an acid, will turn blue litmus paper red, while it has no effect on red litmus. On the other hand, sodium hydroxide, a base, turns red litmus paper blue and either keeps the blue litmus paper blue or makes it more intensely blue. This contrast demonstrates the fundamental difference in the chemical properties of acids and bases.
     
     
5. How do olfactory indicators like vanilla essence and clove oil aid in understanding the chemical properties of acids and bases?
• Answer: Olfactory indicators like vanilla essence and clove oil aid in understanding chemical properties by their change in odor when exposed to acids and bases. For instance, vanilla essence may lose its scent in the presence of a base, while clove oil's scent might change differently. This provides an additional, non-visual means to detect and understand the nature of chemical substances.
  
  
6.  Explain the observations and reactions involved in Activity 2.3, where zinc granules react with dilute sulphuric acid. Mention the significance of passing the gas through soap solution and the purpose of bringing a burning candle near a gas-filled bubble. Lastly, how do the observations in this activity compare when repeated with other acids like HCl, HNO₃, and CH₃COOH?
   • Answer: In Activity 2.3, when zinc granules are added to dilute sulphuric acid, several observations and reactions can be noted:

   1. Observations on the Surface of Zinc Granules: On the surface of zinc granules, you may observe the formation of small bubbles and the appearance of a shiny, metallic surface. This indicates that a chemical reaction is taking place between the zinc and the acid.
      
      
   2. Formation of Gas: As the reaction proceeds, hydrogen gas (H₂) is evolved. This gas can be collected and observed.
      
      
   3. Passing Gas Through Soap Solution: When the evolved hydrogen gas is passed through soap solution, bubbles are formed in the soap solution. This is because hydrogen gas is less dense than air and rises through the soap solution, creating bubbles.
      
      
   4. Burning Candle Near Gas-Filled Bubble: Bringing a burning candle near a gas-filled soap bubble results in a small explosion or a popping sound. This occurs because hydrogen gas is highly flammable, and when ignited, it reacts explosively with oxygen in the air, forming water vapor (H₂O).
      
      
   5. Repeating Activity with Other Acids: When you repeat this activity with other acids like HCl, HNO₃, and CH₃COOH, you will observe similar reactions. The metal (zinc) in each case displaces hydrogen atoms from the acids to form a corresponding salt and release hydrogen gas. The observations in these cases will be similar to those observed with dilute sulphuric acid.
      
      

   The reactions observed in these cases can be summarized as:

   • Acid + Metal → Salt + Hydrogen gas

   For example, for the reaction with dilute sulphuric acid:

   • H₂SO₄(aq) + Zn(s) → ZnSO₄(aq) + H₂(g)

   In conclusion, Activity 2.3 demonstrates the characteristic reaction of metals with acids, producing hydrogen gas and a salt. Passing the gas through soap solution and testing with a burning candle illustrate the flammable nature of hydrogen gas, and the observations are similar when repeated with other acids.

CBSE Class 10 Science Chapter 1 - Chemical Reactions and Equations
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