What weight of oxygen gas will contain the same number of molecules as $56$ g of nitrogen gas? $\left(\mathrm{O}=16\mathrm{u}; \mathrm{N}=14\mathrm{u}\right)$

What mass of nitrogen ${\mathrm{N}}_2$, will contain the same number of molecules as $1.8$ g of water, ${\mathrm{H}}_2\mathrm{O}$? (Atomic masses: $\mathrm{N}=16\mathrm{u}; \mathrm{H}=1\mathrm{u}; \mathrm{O}=16\mathrm{u}$) 

If one gram of sulphur contains x atoms, calculate the number of atoms in one gram of oxygen element. (Atomic mass$: \mathrm{S}=32 \mathrm{u} ; \mathrm{O}=16 \mathrm{u}$)

How many grams of magnesium will have the same number of atoms as $6$ grams of carbon? $(\mathrm{Mg} =24 \mathrm{u}; \mathrm{C}=12 \mathrm{u})$

The mass of one atom of an element X is $2.0\times {10}^{-23}$ g. 

(i) Calculate the atomic mass of element X. 

(ii) What could element X be?