Which of the following has the highest electrode potential?

$A$ metal $M$ readily forms a water-soluble sulphate and a water-insoluble hydroxide $M(OH)_2$. Its oxide $MO$ is amphoteric,hard,and has a high melting point. The alkaline earth metal $M$ must be

The setting of Plaster of Paris involves:

Which one of the following compounds is a peroxide?

Chemical $A$ is used for water softening to remove temporary hardness. $A$ reacts with $Na_2CO_3$ to generate caustic soda. When $CO_2$ is bubbled through $A$,it turns cloudy. What is the chemical formula of $A$?

Which of the following ions has a higher hydration enthalpy than the $Mg^{2+}$ ion?