Which of the following compounds is used for the preparation of quicklime?

Which compound produces a paramagnetic acidic gas upon heating?

Solubility of sulphates of group $2$ elements decreases down the group due to

$(a)$ Give reactivity of alkaline earth metals towards air,water,dihydrogen and acids.
$(b)$ Explain reducing nature of alkaline earth metals.
$(c)$ Give chemical reaction of alkaline earth metals with liquid ammonia.

An element of group $2$ forms a covalent oxide which is amphoteric in nature and dissolves in water to give an amphoteric hydroxide. Identify the element and write chemical reactions of the hydroxide of the element with an alkali and an acid.

What is the substance known as 'blanc fixe' used in paints?