Define complex salts.

Which of the following are the example of double salt?

(A) ${\mathrm{FeSO}}_4·{\left({\mathrm{NH}}_4\right)}_2{\mathrm{SO}}_4·6{\mathrm{H}}_2\mathrm{O}$

(B) ${\mathrm{CuSO}}_4·4{\mathrm{NH}}_3·{\mathrm{H}}_2\mathrm{O}$

(C) ${\mathrm{K}}_2{\mathrm{SO}}_4·{\mathrm{Al}}_2{\left({\mathrm{SO}}_4\right)}_3·24{\mathrm{H}}_2\mathrm{O}$

(D) $\mathrm{Fe}(\mathrm{CN}{)}_2·4\mathrm{KCN}$

Choose the correct answer.

Name the following:

A salt containing a metal ion surrounded by other ions or molecules. 

Choose from the following list of substances, the one substance, that matches the description given below:

Give the names and the formulae of the following:

An acid salts.

Find the odd one out and explain your choice:

$\mathrm{A}:{\mathrm{NaHSO}}_4, \mathrm{B}:{\mathrm{Na}}_2{\mathrm{SO}}_4, \mathrm{C}:{\mathrm{Na}}_2{\mathrm{CO}}_3, \mathrm{D}:{\mathrm{NaNO}}_3$ (Enter your correct answer as $\mathrm{A}, \mathrm{B}, \mathrm{C} \mathrm{or} \mathrm{D}$)

Choose from the following list of substances, the one substance, that matches the description given below:

The compound is used as a preservative.