What chemical compound from the mercury spillage kit is used to make a paste to contain a mercury spillage?

The chemical compound used to make a paste to contain a mercury spillage is calcium hydroxide. This substance reacts with mercury to form a compound that immobilizes it, which is crucial for safe cleanup. Calcium hydroxide can absorb the mercury and help to prevent its spread, reducing the risk of inhalation or exposure, which is particularly important given the hazardous nature of mercury.

In contrast, the other options provided do not serve the same purpose. Calcium sulphate is not typically used for mercury containment, as it does not effectively immobilize or neutralize mercury. Phosphoric acid is an acid that could potentially react with various substances but is not effective at containing mercury spills. Sodium hypochlorite, commonly known as bleach, is used for disinfection but does not immobilize mercury, and can even create hazardous fumes if it interacts with organic materials or certain metals. Thus, calcium hydroxide is the most appropriate and effective choice for creating a paste that safely contains mercury.