SI2 is sulphur diiodide. Sulphur is in group sixteen (six valence electrons) while iodine is in group 17(seven valence electrons).
Since there are two iodine atoms and one sulphur atom, the molecule has twenty valence electrons. Out of these twenty valence electrons, only four are bonding electrons. The other sixteen electrons include the four nonbonding electrons found on sulphur and the twelve non bonding electrons found on the two iodine atoms having six nonbonding electrons each.
Detailed solution is shown in the image attached. The number of moles of NaCl is first obtained. Since the molarity must be in units of molL-1, the volume is divided by 1000 and the formula stated in the solution is applied and the answer is given to one significant figure.
