A student takes about 2 ml of ethanoic acid in a dry test tube and adds a pinch of sodium hydrogen carbonate to it. He reports the following observation:
(I) Immediately a colourless and odourless gas evolves with brisk effervescence.
(II) The gas turns lime water milky when passed through it.
(III) The gas burns with an explosion when a burning splinter is brought near it.
(IV) The gas extinguishes the burning splinter that is brought near it.
Which is the correct observation among the given observations?

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II, III and IV

III, IV, and I

I, II and IV

I, II and III

answer is D.

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Detailed Solution

Observations I, II and IV are correct.
If a student takes about 2 ml of ethanoic acid in a dry test tube and adds a pinch of sodium hydrogen carbonate to it, then immediately a colourless and odourless gas will evolve with a brisk effervescence.

The gas turns lime water milky when it passes through the lime water and the gas extinguishes the burning splinter that is brought near it. The gas is carbon dioxide.

The reaction for the given process is given below:
$C H_{3} COOH + NaHC O_{3} \to C H_{3} CO O^{-} N a^{+} + H_{2} O + C O_{2}$