By heating $32.1 \mathrm{g}$ ammonium chloride with calcium hydroxide $10.2 \mathrm{g} {\mathrm{NH}}_3$ , $33.3 \mathrm{g} {\mathrm{CaCl}}_3$  and $10.8 \mathrm{g} {\mathrm{H}}_2\mathrm{O}$ are obtained. How many grams of calcium hydroxide take part in the reaction? How many moles of ${\mathrm{NH}}_3$ and how many litres of ${\mathrm{NH}}_3$, at STP is formed at the reaction? 

According to the following chemical equation,

${\mathrm{CH}}_4+2{\mathrm{O}}_2\to {\mathrm{CO}}_2+2{\mathrm{H}}_2\mathrm{O}$

what volume of ${\mathrm{O}}_2$ will be required to burn $10$ mole of ${\mathrm{CH}}_4$ at STP?

A and B react to produce C according to the following chemical equation 
$2\mathrm{A} + \mathrm{B} \to 2\mathrm{C}$

A, B and C are the formulas for three gaseous substances. The vapour densities of A and B are 32 and 16 respectively. Find out the vapour density of C. 

According to the following chemical equation:

$2\mathrm{ZnS} + 3{\mathrm{O}}_2 \to 2\mathrm{ZnO} + 2 {\mathrm{SO}}_2$

from 100 mole of $\mathrm{ZnS}$

(i) how many gram of $\mathrm{ZnO}$, and

(ii) how many mole of ${\mathrm{SO}}_2$, will be produced ? 
($\mathrm{Zn}=65.5, \mathrm{S} = 32, 0 = 16$)