Let's start with the skeleton equation:
KClO_3 -> KCl + O_2KClO3→KCl+O2
Then, balance both sides:
2KClO_3 -> 2KCl + 3O_22KClO3→2KCl+3O2
From this, we know that 22 moles of KClO_3KClO3 corresponds to 33 moles of O_2O2. That means we just need to find out the number of moles of O_2O2 in "200g"200g to see how many moles of KClO_3KClO3 decomposed!
The mass of one mole, or the molar mass, of O_2O2 is 16.00+16.00="32.00g"16.00+16.00=32.00g, because the mass of one mole of OO is "16.00g"16.00g.
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So, "200g"200g of O_2O2 is:
200/32.00="6.25 moles"20032.00=6.25 moles
Again, 33 moles of O_2O2 corresponds to 22 moles of KClO_3KClO3.
Therefore, "6.25 moles"6.25 moles of O_2O2 corresponds to 2*6.25/3="4.16666667 moles"2⋅6.253=4.16666667 moles of KClO_3KClO3.
Finally, because the question had 11 significant figure, our answer is "4 moles"4 moles.