Question

aqueous solution of which of the following oxides turns blue litmus into red. sulphur dioxide, mg,iron oxide or copper oxide

Answer 1

Sulphur is a non-metal and it forms an acidic oxide, i.e. sulphur dioxide (SO2)which turns blue litmus red.

Answer 2

We know that acidic oxides of non-metals turn the blue litmus paper to red and metallic oxides that are basic turns the red litmus blue.  

In the given options sulphur dioxide (SO2) will turn the blue litmus red as sulphur is a non-metal and therefore its oxide is also non-metal.

Litmus papers are used to find the characteristics of acidic or basic nature of any solution.