First, we have to convert from 195 grams of KClO3 to moles, using its molar mass which you can calculate it using the periodic table (122.5 g/mol):
[tex]195gKClO_3\cdot\frac{1\text{ mol }KClO_3}{122.5\text{ g }KClO_3}=1.59\text{ mol }KClO_3.[/tex]
Now that we have this value, we can find the number of moles produced of oxygen doing a rule of three taking into account that 2 moles of KClO3 produces 3 moles of oxygen:
[tex]\begin{gathered} 2\text{ moles }KClO_3\to3molesO_2 \\ 1.59\text{ moles }KClO_3\to?molesO_2 \end{gathered}[/tex]
And the calculation would be:
[tex]1.59\text{ moles }KClO_3\cdot\frac{3molesO_2}{2\text{ moles }KClO_3}=2.39molesO_2.[/tex]
The final step is to convert 2.39 moles of oxygen to grams using its molar mass. The molar mass of oxygen (O2) is 32 g/mol:
[tex]2.39molesO_2\cdot\frac{32gO_2}{1molO_2}=76.4gO_2.[/tex]
The answer is that 195 grams of KClO3 decomposed, produces 76.4 grams of oxygen (O2).
