Question

# When a red litmus paper is dipped in the aqueous solution of X there is no change in colour. When a blue litmus paper is dipped in the same solution it turns red. Which among the following options can be the chemical X?

A

Na2O

B

SO2

C

MgO

D

CaO

Solution

## The correct option is C SO2 We are given that the product made by reacting chemical X with water did not react with red litmus paper it could be a neutral substance or an acidic substance. The next information tells us that the blue litmus turns red when it is dipped in the product, therefore, the product given to us is acidic in nature.  Among the given options only SO2 gas can mix with water to produce an acidic solution of sulphuric acid. All other options are metallic oxides which produce basic solutions, therefore, cannot be the correct answer. Hence the chemical X is SO2

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