What is the common name for unslaked lime?

The correct answer is quicklime. Unslaked lime refers to calcium oxide (CaO), which is produced by heating limestone (calcium carbonate) in a process called calcination. When limestone is heated, it produces quicklime. This substance is called "unslaked" because it has not yet been reacted with water. Quicklime is highly reactive and can be used in various applications, including water treatment, construction, and soil stabilization.

Hydrated lime, which is sometimes confused with quicklime, is actually calcium hydroxide (Ca(OH)₂) and is produced by adding water to quicklime, a process known as slaking. This distinction is important in understanding the chemistry and applications of lime in various fields, including water treatment.

Options involving lime hydrate and calcium hydroxide pertain to the product after quicklime has been hydrated, further differentiating them from unslaked lime's original state.