posted by kayla on .
If 267 mL of O2, measured at STP, are obtained by the decomposition of the KClO3 in a 3.33 g mixture of KCl and KClO3, 2KClO3(s) --> 2KCl(s) + 3O2
What is the percent by mass of KClO3 in the mixture?
Given that 1 mole of any gas occupies 22.4 litres at STP you can calculate the number of moles of O2 in 267 ml, (F moles)
2KClO3(s) --> 2KCl(s) + 3O2
tells you that 3 moles of O2 came from 2 moles of KClO3, therefore you can work out how many moles of KClO3 would be needed to yield F moles of O2
number of moles of KClO3
Calcluate the molar mass of KClO3, M.
Thus the mass of KClO3 needed is
Hence the percentage of KClO3 in the mixture is