Illustrate the role of sodium and potassium in biological fluid

How is sodium hydroxide prepared commercially from brine solution?

Compare the properties of beryllium with other elements of the same group.

Explain the preparation and uses of the following compounds of calcium.

When water is added to compound (A) of calcium, compound B is formed with a hissing sound and evolution of large amount of heat. When CO₂ is passed into the solution, it turns milky due to the formation of compound C. If excess CO₂ is passed into the solution, milkiness disappears due to the formation of compound (D). Identify the compounds A, B, C and D. Explain why the milkiness disappears in the last step.