Chemistry 2005 JAMB Past Questions - Question 19: When water boilers are used for a iong period of time, the solid substances left behind as scale

Correct Answer

D

Explanation

When water boilers are used for a long period of time, the solid substances left behind as scale typically consist of minerals and impurities that precipitate out of the water as it is heated and evaporated. The exact composition of the scale can vary depending on the water source and the specific minerals present. Common components of scale include calcium carbonate, magnesium carbonate, and other minerals.

The compounds you mentioned, such as magnesium trioxosilicate (IV), rust, calcium tetraoxosulphate (VI), and clay, are not commonly found as primary components of boiler scale. However, rust (iron oxide) can be present in the form of corrosion products if the boiler or the water supply system contains iron or if there is corrosion of metal components.

It's important to note that the composition of boiler scale can vary, and it is typically a complex mixture of minerals and substances that were dissolved in the water. Regular maintenance and water treatment are essential to minimize scale formation in boilers and ensure efficient operation.