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. 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.

ScienceCBSE Class 10 · Sample paper, session 2026-27 · 3 marks · Short answer

CBSE Class 10 Science sample paper 2026-27: question 27

From the official CBSE sample question paper for 2026-27, section B, question 27, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q27 · 3 marks · Short answerAcids, Bases and Salts

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.

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

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2026-27.

Hints

Open one hint at a time and try again before the next.

Hint 1

Electric current through a liquid needs charged particles that can move.

Hint 2

Consider the product formed first with $C O_{2}$ and what happens to it when more $C O_{2}$ and water are present.

Hint 3

List the two conditions iron needs to rust, and ask which one differs between the two places.

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

A. A sports electrolyte drink contains dissolved salts that exist as free ions (such as $N a^{+}$ , $K^{+}$ and $C l^{-}$ ). These ions carry current, so the drink conducts electricity. Coconut oil is made of covalent molecules and has no ions, so it does not conduct.
1 mark
B. Passing $C O_{2}$ forms insoluble calcium carbonate, which makes the lime water milky:
$Ca (OH)_{2} (aq) + C O_{2} (g) \to CaC O_{3} (s) + H_{2} O (l)$
With excess $C O_{2}$ , the carbonate changes into soluble calcium hydrogen carbonate, so the milkiness disappears:
$CaC O_{3} (s) + H_{2} O (l) + C O_{2} (g) \to Ca (HC O_{3})_{2} (aq)$
1 mark
C. Rusting needs both oxygen and moisture. Air near the sea is very humid and carries salt, which speeds up rusting. Air in a dry hilly region has little moisture, so rusting there is much slower.
1 mark

Answer: A. The drink has free ions; coconut oil has none. B. Excess $C O_{2}$ converts insoluble $CaC O_{3}$ into soluble $Ca (HC O_{3})_{2}$ . C. High humidity (and salt) near the sea speeds up rusting; dry hill air has little moisture.

Where the marks are

States that the drink has ions (electrolytes) and coconut oil has none (1 mark)
Insoluble $CaC O_{3}$ causes milkiness and changes to soluble $Ca (HC O_{3})_{2}$ with excess $C O_{2}$ (1 mark)
High moisture near the sea speeds rusting; low moisture in dry hills slows it (1 mark)

Revise the chapter

Chapter: Acids, Bases and Salts (notes, formulas, where marks are lost and every past question)

Practise this chapterBoard-style questions from Acids, Bases and Salts, one at a time, marked against the answer key and marking points.Back to the full paperSample paper 2026-27: every question, by section.

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CBSE Class 10 Science sample paper 2026-27: question 27

Hints

Step-by-step solution

Revise the chapter

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