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Question:

A student takes 2 mL acetic acid in a dry test tube and adds a pinch of sodium hydrogen carbonate to it. He makes the following observations: I. A colourless and odourless gas evolves with a 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. The correct observations are:

I, II, and III

II, III and IV

III, IV and I

IV, I and II

Solution:

The correct option is D IV, I and II

When acetic acid reacts with sodium hydrogen carbonate, CO2 gas is released. The gas is odorless and colorless and evolves with brisk effervescence.

CO2 turns lime water milky when passed through it due to the formation of calcium carbonate.

The burning splinter extinguishes when the gas is brought near it as it does not support combustion and is not flammable.