Number of water molecules in Mohr's salt is

The sum of the number of water molecules present in Mohr's salt and potash alum is "a" what is "3a" ?

What is Mohr's salt ?

The number of water molecules present in Glauber's salt is _________.

Consider a titration of potassium dichromate solution with acidified Mohr's salt solution using diphenylamine as indicator. The number of moles of Mohr's salt required per mole of dichromate' is