What is the mass in gram of one molecule of caffeine $\left({\mathrm{C}}_8{\mathrm{H}}_{10}{\mathrm{N}}_4{\mathrm{O}}_2\right)$?

Calculate the number of moles of sulphur in $64 \mathrm{g}$ of sulphur.

Note: This question was incomplete.

Round up the following upto three significant figures.

$10.4107$

$32 \mathrm{g}$ of sulphur reacts with $32 \mathrm{g}$ of oxygen even if more than $32 \mathrm{g}$ of sulphur are available. Which law of chemical combination does this illustrate?

Give the empirical formula of the following substance. 

${\mathrm{C}}_6{\mathrm{H}}_6$

Give the empirical formula of the following substance. 

Graphite

Give the empirical formula of the following substance. 

Magnesium chloride