Write the chemical formula using criss-cross method.

Ammonium sulphate

Write the chemical formula using criss-cross method. 

Magnesium bicarbonate

Write chemical formula using criss-cross method.

Barium nitrate

Calculate the number of moles of Sulphur $\left({\mathrm{S}}_8\right)$ present in $16$g of solid sulphur.

Calculate the mass of $10$ moles of sodium sulphite$\left({\mathrm{Na}}_2{\mathrm{SO}}_3\right)$.

Calculate the number of atoms in $11.5$g of $\mathrm{Na}$.

$\left[\mathrm{atomic} \mathrm{mass}; \mathrm{Na}=23 \mathrm{u}, \mathrm{S}=32 \mathrm{u},\mathrm{O}=16 \mathrm{u}, {\mathrm{N}}_{\mathrm{A}}=6.022\mathrm{x}{10}^{23} {\mathrm{mol}}^{-1}\right]$