Potassium perchlorate, KCIO_4, decomposes on heating to form potassium chloride

Question

Potassium perchlorate, KCIO_4, decomposes on heating to form potassium chloride and elemental oxygen. Write a balanced molecular equation for the thermal decomposition of potassium perchlorate. Using a setup like this experiment, the following data were collected mass of sample before heating 2.6865 g mass of residue after heating 2.0475 g volume of water displaced 516 mL atmospheric pressure 750.7 torr water temperature 27.0 degree C What is the percent mass KCIO_4 in the sample being heated? What volume would this sample of oxygen occupy if collected at standard temperature and pressure? What is the molar volume at STP of O_2 according to these data?

Explanation / Answer

3. a 2KClO4 ==> 2KCl + 4O2

b. mass reduced = 2.6865-2.0475= 0.639 gm

% mass KClO3 = (0.639/2.6865 ) * 100 =23.79 %

c. volume of O2 at this temperature = 516 mL = 0.516

P = 750.7 torr = 0.988 atm

moles of O2 at this temperature = PV/RT = 0.988 atm * 0.516 L /0.082Latm/K/mol * 300 K = 0.021 mol

volume of gas at 25oC and 1 atm pressure = nRT/P

                                                              =0.021 *0.082 Latm/K/mol *298/1 atm =0.506 L

(d) Molar volume = 0.506/0.021 =24.11 L

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