4) The test tube and contents should be heated again for an additional three min

Question

4) The test tube and contents should be heated again for an additional three minutes, cooled, and re-weighed. If this weight agrees within 0.01 grams of the previous one, you may assume that all of the oxygen has been driven off. Otherwise, another heating is necessary. This is called heating to a constant weight and is done by chemists in all precise work. When the weight is constant, record your data. 5) After the test tube is cool, rinse the salt out of the test tube using tap water and a test tube brush and return them to their original container. The product solid and any rinse solution may be discarded down the drain. 22.75 DATA: aK CCio Mass of empty test tube 2) Mass of Test tube and contents before heating Mass of potassium chlorate used 2.02 g Mass of test tube and contents after heating to constant wt. 393 Mass of potassium chloride produced Experimental Mass of oxygen driven off Theoretical mass of oxygen produced casos ro Lg Lg Error Percent error Calculations: 1. Calculate the theoretical mass of oxygen in your sample of potassium chlorate. Show equation!!!! 2. Calculate your experimental and percent error and indicate if your results are too high or too low.

Explanation / Answer

2KClO3 --> 2KCl + 3O2

mass of KClO3 = 2.0 g

moles KClO3 = 2.0 g/122.55 g/mol = 0.0163 moles

theoretical moles of O2 produced = 0.0163 moles x 3/2 = 0.025 moles

theoretical mass of O2 produced = 0.025 moles x 32 g/mol = 0.8 g

mass of KCl formed = 0.81 g

Therefore here the mass of O2 formed experimentally is much higher than the actual value. Their is an error in measurement of origjnal KClO3 mass or the final mass KCl formed. The values must be rechecked again. the experimental mass of O2 cannot be greater than theorectial mass of O2.

Actual mass of O2 produced = 2.02 - 0.81 = 1.19 g

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