A white solid is either Na $_{2}$ O or Na $_{2}$ O $_{2}$ . A piece of red litmus paper turns white when it is dipped into a freshly made aqueous solution of the white solid.
The molecular mass of the substance is:

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Solution

The white solid is Na $_{2}$ O $_{2}$ .
A piece of red litmus paper turns white when it is dipped into a freshly made aqueous solution of the white solid.
(i) Na $_{2}$ O $_{2}$ + 2H $_{2}$ O $\to$ + H $_{2}$ O + [O][O] + Litmus $\to$ White (due to the bleaching effect of nascent oxygen).
(ii) The other compound Na $_{2}$ O will give NaOH on dissolution in water. The red litmus will turn to blue.
Hence, the molecular mass of the substance is 78 g/mol.

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A white solid is either Na2O or Na2O2. A piece of red litmus paper turns white when it is dipped into a freshly made aqueous solution of the white solid.The molecular mass of the substance is:

A white solid is either Na $_{2}$ O or Na $_{2}$ O $_{2}$ . A piece of red litmus paper turns white when it is dipped into a freshly made aqueous solution of the white solid.
The molecular mass of the substance is: