question_answer

    Samuel had a Silver coin which turned black. He kept the coin in a bowl lined with aluminium foil. Then he filled the bowl with waterand boiled it. After sometime, he found that the coin has become new. Its blackness disappeared. How did it happen?

Answer:

                  The blackness of silver coin is due to the formation of silver sulphide on its surface. On boiling, the aluminium foil reacts with the layer of silver sulphide thus making it shiny. 3Ag2S + 2Al   6Ag + AI2S3