Question

Rathika brought the pictures of two metal samples to her chemistry lab and displayed them. She told her classmates that these metal samples occur in free state and do not corrode easily. The chemistry teacher told her students that corrosion is not always a destructive phenomenon and the corrosion of some metals is advantageous also. (a) Identify the metal samples in the pictures brought by Rathika. (b) With a suitable example, explain how corrosion is advantageous.

Answer 1

Answer:

A chemistry student trying to detect the metallic ion in a salt makes a paste on the clean Pt wire-loop of the salt with concentrated HCl. When he takes a small amount of this paste and keeps it in a non-luminous Bunsen flame, the color of the flame changes to grassy green. He should , therefore, conclude that the metal is Barium (Ba). The table below gives a rough color guide for the elements.

Flame color :

Li= red

Na= strong, persistent orange

K= lilac (pink)

Rb= red (red-violet)

Cs= blue/violet (see below)

Ca= orange-red

Sr= red

Ba= pale green

Cu= blue-green (often with white flashes)

Pb= gray-white