LIWA

Acids, Bases and Salts

CBSE Class 10 · Science · Chapter 2

Past board exam questions

CBSE 2027 sample paper · 1 mark

Rishita summarizes the chlor-alkali process in the following table. | Option | Product | Formed | Use | |---|---|---|---| | I | Hydrogen | At cathode | Used as a fuel | | II | Chlorine | At anode | Used to make margarines | | III | Sodium Hydroxide | Near cathode | To make soap | | IV | Sodium Hydroxide | Near anode | To make bleaching powder | Identify the options that are correctly matched.

  1. I, II and III
  2. I and III
  3. II and IV
  4. I, II, III and IV
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I and III

CBSE 2027 sample paper · 1 mark

Which of the following salts contain water of crystallisation: (i) Plaster of Paris, (ii) Washing soda, (iii) Baking soda and (iv) Gypsum.

  1. (i), (ii) and (iii)
  2. (i), (iii) and (iv)
  3. (ii), (iii) and (iv)
  4. (i), (ii) and (iv)
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(i), (ii) and (iv)

CBSE 2027 sample paper · 1 mark

Assertion (A): Onion extract loses its smell, when it is added to baking soda solution whereas it retains its smell when added to lemon juice. Reason (R): Onion acts as an olfactory indicator.

  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, and R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.
Show answer
Both A and R are true, and R is not the correct explanation of A.

CBSE 2027 sample paper · 3 marks

Give reason for the following : A. A solution of sports electrolyte drink conducts electricity, but coconut oil does not. B. Milkiness disappears when excess of carbon dioxide is passed through lime water. C. An iron bridge near the sea rusts much faster than an iron bridge located in a dry hilly region.

Show answer
A. A sports drink contains ions (electrolytes) which conduct electricity. Coconut oil does not contain ions, so it cannot conduct electricity. B. Lime water turns milky due to the formation of insoluble calcium carbonate: Ca(OH)₂ + CO₂ → CaCO₃ + H₂O. When excess CO₂ is passed, calcium carbonate reacts further to form soluble calcium hydrogen carbonate, CaCO₃ + H₂O + CO₂ → Ca(HCO₃)₂, so the milkiness disappears. C. Rusting needs both oxygen and moisture. Air near the sea contains high moisture (humidity) and salt, which speed up rusting. In a dry hilly region the moisture is low, so rusting occurs much more slowly.

CBSE 2026 board paper · 1 mark

Tamarind is a natural source of which acid ?

  1. Acetic acid
  2. Tartaric acid
  3. Oxalic acid
  4. Citric acid
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Tartaric acid

CBSE 2026 board paper · 1 mark

Tomato is a natural source of which acid ?

  1. Acetic acid
  2. Tartaric acid
  3. Oxalic acid
  4. Citric acid
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Oxalic acid

CBSE 2026 board paper · 1 mark

Which one of the following can be used as an acid-base indicator by a blind student ?

  1. Turmeric
  2. Vanilla essence
  3. Methyl orange
  4. Litmus
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Vanilla essence

CBSE 2026 board paper · 1 mark

Rain water is called ‘acid rain’ when its :

  1. pH falls below 7·2.
  2. pH falls below 14.
  3. pH is above 7.
  4. pH falls below 5·6.
Show answer
pH falls below 5·6.