We have the following balanced reaction:
[tex]2S+3O_2\rightarrow2SO_3[/tex]
The ratio mol O2/mol S is 3/2. Now, we are given the grams of S, with this information we can calculate the moles of O2 needed in the following way:
[tex]\begin{gathered} molO_2=\text{Given g of S }\times\frac{\text{1mol S}}{\text{Molar mass of S}}\times\frac{3\text{ mol O2}}{2\text{ mol S}} \\ molO_2=5.93g\text{ of S}\times\frac{\text{1mol S}}{\text{32.065 g of S}}\times\frac{3\text{ mol O2}}{2\text{ mol S}} \\ molO_2=0.28\text{mol} \end{gathered}[/tex]
Now, to calculate the molecules we will apply the Avogadro's number:
[tex]\begin{gathered} \text{Molecules of O}_2=0.28\text{mol}\times\frac{6.022\times10^{23}molecules}{1\text{ mol}} \\ \text{Molecules of O}_2=1.67\text{ }\times10^{23}molecules \end{gathered}[/tex]
So, it would be needed 1.67x10^23 molecules of O2 to react with 5.93 g of S
