Calculate the number of moles in $90 \text{ g}$ of water. (in $\text{ moles}$)

Which of the following species have $18$ electrons? $Ca^{2+}, K^{+}, Na, Cl^{-}, Ar$. Also,state the reason why the chemical properties of all isotopes of an element are similar.

Calcium chloride when dissolved in water dissociates into its ions according to the following equation:
$CaCl_{2}(aq) \rightarrow Ca^{2+}(aq) + 2Cl^{-}(aq)$
Calculate the number of ions obtained from $CaCl_{2}$ when $222 \, g$ of it is dissolved in water.

$3.42 \, g$ of sucrose are dissolved in $18 \, g$ of water in a beaker. The number of oxygen atoms in the solution are

Calculate the molecular mass of the following compounds:
$(i)$ $NH_{4}NO_{3}$
$(ii)$ $H_{2}SO_{4}$
$(iii)$ $Na_{2}CO_{3}$
$(iv)$ $NaOH$
$(v)$ $HNO_{3}$
$(vi)$ $Al_{2}(SO_{4})_{3}$

Give one example each of:
$(a)$ Triatomic element
$(b)$ Monoatomic molecule
$(c)$ Polyatomic element
$(d)$ Polyatomic ion