Question

A ribbon of silvery white element when heated in flame , burns with a dazzling white light and leaves a white powder .The white powder dissolved in water turns red litmus blue. Answer following question

Answer 1

This your question seems to be incomplete but I would like to have a look at it in details.

A ribbon of the silvery white element when heated in a flame burns with a dazzling white light and leaves a white powder .The white powder dissolved in water turns red litmus blue.

What you can gather from the question itself is that after combustion the powder which remains is soluble in water and on the other hand it turns red litmus blue. This implies that the solution that is resulting is basic in nature and that is the reason as to why it turns red litmus blue.