Question

You need to weigh your own large Pyrex test tube and know the empty mass, mass with KCIO3 mixture bet heating; mass with KCIO, mixture and catalyst and mass of all of the above after heating. To weigh the test tube, place it in an empty beaker to keep it upright. You may tare the weight of the bea you need to know the weight of the test tube for your calculations. Procedures: Weigh your clean, dry empty Pyrex test tube (1) Obtain the unknown KCIO, mixture from the storeroom and weigh out about 1.4 grams in your test tube ( After weighing unknown sample, go to the storeroom to obtain the catalyst, MnO2. Mix it thoroughly with unknown and then weigh the test tube again. (3) After thoroughly heating the mixture and no more water is being displaced, weigh the test tube mixture ( Unlined data is obtained indirectly for your calculations Data 1. Weight of your empty Pyrex test tube 2. Weight of KCLO3 mixture and your test tube 32.1576 - grams 36.9550 4.7960 00 Mass of the unknown mixture of KCLO; (2-1) b 3. Weight of the unknown mixture, test tube with thoroughly mixed catalyst 01.110 69 4. Weight of the unknown mixture, test tube and catalyst after heating bu Mass lost by heating (also mass of gas produced) (3-4) 36.91938 0.33 Kelvin 5. Temperature of the gas produced_1998 _°C 292.95 6. Volume of the gas collected 13 ML 7. Barometer reading (uncorrected at 24.2 °C) 90 _mm Hg 8. Corrected barometric pressure due to mercury expansion 7874_mm Hg 9. Vapor pressure of water at the temperature of the gas (from the table) Die mm Hg Vapor pressure of the oxygen collected (8-9) mm Hg

Answer 1

1) Mass of gas produced = 0.1333 g

2) Partial pressure of gas = 787.4-18.6

= 768.8 torr (1mmHg = 1 torr)

3) P = 768.8 torr , V = 113 ml = 0.113 L, T = 292.95 K

Using ideal gas law, moles, n = PV/RT

R = 62.364 Ltorr/Kmol.

Moles,n = 768.8×0.113/62.364×292.95

= 0.00475 moles

4) Experimental molecular weight = mass/moles

= 0.1333/0.00475

= 28.06 g/mol

5) percent error

=(mass of oxygen-calculated)×100/mass of oxygen

= (32-28.06)×100/32

= 12.31%