Class 10 Science · Chapter 4

Carbon and its Compounds

442 Class 10 Science questions on Carbon and its Compounds from the NCERT textbook, NCERT Exemplar and CBSE board papers 2017–2026, each with its answer and a step-by-step solution.

CBSE Class 10 Science previous year papers, with answers →

Questions · page 23 of 23

1. Q441 CBSE 2017
   What do you observe when you pour a ​few drops of ​acetic acid to ​a test tube containing (A) ​Distilled water ? (B) Red litmus solution ? (C) Blue ​litmus ​solution ​? (D) Universal ​indicator ?
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   It dissolves in water, leaves red litmus unchanged, turns blue litmus red and turns universal indicator orange.

   (A) The acid dissolves completely: a clear, colourless solution forms, with no separate layer. (B) No change: the red litmus solution stays red. (C) The blue litmus solution turns red, showing that acetic acid is an acid. (D) The universal indicator turns orange (pH about 3 to 4), showing an acidic solution; it is not the deep red of a strong acid, because acetic acid is a weak acid.

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2. Q442 CBSE 2017
   What ​do ​you ​observe when you ​add ​sodium ​bicarbonate to ​acetic acid ? ​How would you identify the gas released in the reaction ? Describe briefly.
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   Brisk effervescence occurs; the colourless gas turns lime water milky, so it is carbon dioxide.

   Observation: a brisk effervescence, as bubbles of a colourless gas are given off: ${\text{CH}}_3\text{COOH}+{\text{NaHCO}}_3⟶{\text{CH}}_3\text{COONa}+{\text{H}}_2\text{O}+{\text{CO}}_2$. Identification: pass the gas through a delivery tube into lime water. The lime water turns milky because carbon dioxide forms insoluble white calcium carbonate: ${\text{Ca(OH)}}_2+{\text{CO}}_2⟶{\text{CaCO}}_3+{\text{H}}_2\text{O}$. So the gas is carbon dioxide.

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