Chapter 2.7, Problem 4CP

What is the formula of nickel(II) nitrate hexahydrate?

$\begin{array}{l}\text{a)}\\ {\text{NiNO}}_{\text{3}}{\text{ 6H}}_{\text{2}}\text{O}\\ \text{b)}\\ {\text{Ni}}_{\text{2}}{\text{NO}}_{\text{3}}{\text{ 6H}}_{\text{2}}\text{O}\\ \text{c)}\\ \text{Ni}{\left({\text{NO}}_{\text{3}}\right)}_{\text{2}}{\text{ 6H}}_{\text{2}}\text{O}\\ \text{d)}\\ {\text{NiNO}}_{\text{3}}{\text{ 12H}}_{\text{2}}\text{O}\\ \text{e)}\\ \text{Ni}{\left({\text{NO}}_{\text{3}}\right)}_{\text{2}}{\text{12H}}_{\text{2}}\text{O}\end{array}$