Calculate the number of water molecules present in one drop of water which weighs $0.18\mathrm{g}$. 

${\mathrm{N}}_2+3{\mathrm{H}}_2\to 2{\mathrm{NH}}_3$

(The atomic mass of nitrogen is $14$, and that of hydrogen is $1$) 

$1$ mole of nitrogen (_____ $\mathrm{g}$) + $3$ moles of hydrogen (_____ $\mathrm{g}$)$\to$ $2$ moles of ammonia (_____ $\mathrm{g}$)

Calculate the number of moles in 

i) $27\mathrm{g}$ of $\mathrm{Al}$

ii) $1.51\times {10}^{23}$ molecules of ${\mathrm{NH}}_4\mathrm{Cl}$. 
 

Give the salient features of "Modern atomic theory". 
 

Calcium carbonate is decomposed on heating in the following reaction:  

${\mathrm{CaCO}}_3\to \mathrm{CaO}+{\mathrm{CO}}_2$

How many moles of Calcium carbonate is involved in this reaction? 
 

Calcium carbonate is decomposed on heating in the following reaction 

${\mathrm{CaCO}}_3\to \mathrm{CaO}+{\mathrm{CO}}_2$

Calculate the gram molecular mass of calcium carbonate involved in this reaction. 

Calcium carbonate is decomposed on heating in the following reaction 

${\mathrm{CaCO}}_3\to \mathrm{CaO}+{\mathrm{CO}}_2$

How many moles of ${\mathrm{CO}}_2$ are there in this equation? 
 

How many grams are there in the following? 

$2$ moles of hydrogen molecule, ${\mathrm{H}}_2$.