Question

129 Seveh dn 133 Name Locker Number Dete Peme pri t REPORT SHEET Experiment 9 Analysls of a KCIO,-KCI Mbture Unknown number 14 Trial 2 is to be performed if Trial 1 is unsatisfactory. Rame mber, units must be used. Trial I Trial I1 32.2124 20.129% Mass of test tube + MnO, + unknown. Mass of test tube + MnO Mass of test tube + MnO, + glass wool (optional) Mass of unknown Mass of test tube + MaO, + residue... 33-9669 .after first heating ...after second heating after third heating Mass of axygen evolved Mass of KCIO, in unknown (Pleaso clearly show all calculations below ar on the back of this page.) Mass of KCl in unknown Percent of KCIO, in unknown. Percent of KCl in unknown

Answer 1

Reaction: 2KClO3(s) --heat--> 2KCl(s) + 3O2(g)

Mass of oxygen evoloved = 33.866 - 33.796 = 0.07 g

Moles of oxygen = 0.07 g/(32 g.mol^-1) = 0.0021875 mol

The mole ratio KClO3:O2 = 2:3

i.e. The moles of KClO3 = 2/3 * 0.0021875 mol = 0.0014583 mol

i.e. The mass of KClO3 = 0.0014583 mol * 122.6 g/mol = 0.179 g

i.e. The percent of KClO3 in unknown = {0.179 g/(33.212-30.789) g}*100 = 7.39%

Now, The mole ratio KCl:O2 = 2:3

i.e. The moles of KCl = 2/3 * 0.0021875 mol = 0.0014583 mol

i.e. The mass of KCl = 0.0014583 mol * 74.6 g/mol = 0.109 g

i.e. The percent of KCl in unknown = {0.109 g/(33.212-30.789) g}*100 = 4.50%