How many atoms are there in $0.25$ mole of hydrogen ? 

Calculate the number of molecules present in a drop of chloroform $\left({\mathrm{CHCl}}_3\right)$ weighing $0.0239 \mathrm{g}$. (Atomic masses : $\mathrm{C}=12 \mathrm{u}; \mathrm{H}=1\mathrm{u}; \mathrm{Cl}=35.5 \mathrm{u}$) 

What is the mass of $5$ moles of sodium carbonate $\left({\mathrm{Na}}_2{\mathrm{CO}}_3\right)$? (Atomic masses: $\mathrm{Na}=23 \mathrm{u}; \mathrm{C}=12 \mathrm{u}; \mathrm{O}=16 \mathrm{u}$) 

How many moles are represented by $100 \mathrm{g}$ of glucose, ${\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6$? $(\mathrm{C}=12 \mathrm{u}, \mathrm{H}= 1 \mathrm{u}, \mathrm{O}=16 \mathrm{u})$

Calculate the mass in grams of $0.17$ mole of hydrogen sulphide, ${\mathrm{H}}_2\mathrm{S}$. (Atomic masses : $\mathrm{H}=1 \mathrm{u}, \mathrm{S}=32 \mathrm{u}$) 

Calculate the mole ratio of $240 \mathrm{g}$ of calcium and $240 \mathrm{g}$ of magnesium. $(\mathrm{Ca}=40 \mathrm{u} ; \mathrm{Mg}=24 \mathrm{u})$