39.8g of a mixture of potassium chloride, KCl, and potassium trioxochlorate(V), KClO3, were heated to a constant mass. If the residue weighed 28.9g, what was the percentage mass of the potassium chloride in the mixture? ( K = 39, Cl = 35.5, O = 16) HINT: KCl is not decomposed on heating.

Answer 1

Your name for KClO3 is not approved by the IUPAC and is incorr
39.8 g = mass KCl + mass KClO3(mass KCl + oxygen)
-28.9 g = mass KCl + mass KCl (oxygen is gone)
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10.9 g = mass oxygen
2KClO3 ==> 2KCl + 3O2
mols O2 = 10.9/32 = approx 0.341
mols KClO3 initially = 0.341 x (2 mols KClO3/3 mols O2) = 0.341 x 2/3) = 0.227 mols KClO3
Then g KClO3 initially = 0.227 x 122.5 = 27.8 g
Then 39.8 g - 27.8 g = 12 g KClO3.
Then % KClO3 = (mass KClO3/39.8)*100 = ?
%KCl initially in the mixture = 100%-%KClO3 = ?