a mixture of 39.8g containing potassium chloride and potassium trioxochlorate (v) upon heating, the residue weighed 28.7g what is the percentage mass of potassium chloride in the residue?

Answer 1

2KClO3 ==> 2KCl + 3O2

mass O2 released = 39.8-28.7 = 11.10g
mols O2 released = grams/molar mass
Using the coefficients in the balanced equation, convert mols O2 to mols KClO3.
Now convert mols KClO3 to grams KClO3. That's g KClO3 = mols KClO3 x molar mass KClO3. grams KClO3 = x
(% KClO3 in the original sample) = (x g KClO3/mass mixture)* 100 = ?