Reaction takes place is
2KClO3 --> 2KCl + 3O2
from above equation 2 moles of potassium chlorate is forming 3 moles of Oxygen gas.
now given 6.83 moles of oxygen and moles of potassium chlorate is missing,
consider x moles of potassium chlorate are needed to form 6.83 moles of oxygen
from above condition, .
3 》》》》2
x 》》》》6.83
3/x = 2/6.83
x = 3×6.83/2
x= 10.245
Answer- 10.245 moles of potassium chlorate are needed to produce 6.83 moles of oxygen gas.