A road tanker carrying an acid was involved in an accident and its contents spilled on the road. At the side of the road, iron drain covers began melting and fizzing as the acid ran over them. A specialist was celled to se if the acid actually leaked into the nearby river.
(a) Explain how the specialist could carry out a simple test to see if the river water contains some acid or not.
(b) The word 'melting' is incorrectly used in the report. Suggest a better name that should have been used for the same purpose.
(c) Explain why the drain covers began fizzing as the acid ran over them.

Explanation

(a) This can be done by adding a strip of blue litums paper into the tube containing a small amount of the sample water. If the colour changes to red, this means that some acid has gone into the river.
(b) The acid has reacted chemically with the drain cover which is usually made of iron. The correct word for the reaction is 'corrosion' and not 'melting'.
(c) Iron reacts with an acid `(H_(2)SO_(4)` or HCl etc.) to evolve hydrogen gas. Since the gas is released immediately accompanied by large number of bubbles, fizzing of drain covers is expected.