# Law of Definite Proportions

1. Calculate and record the following for the experiment performed with 20g KClO3:

(a) mass of the crucible with manganese(IV) dioxide (in grams): 53.300g

(b) mass of the crucible after potassium chlorate has been added (in grams): 73.300g

(c) mass of the crucible after heating (in grams): 21.00 degrees C

(d) mass of potassium chloride (in grams): 8.64

(e) mass of oxygen in sample of potassium chlorate (in grams): 65.367g

(f) mass percent of oxygen in potassium chlorate:

2. Calculate a theoretical mass percent of oxygen in KClO3 according to:

theoretical mass percent of oxygen = (mass of 3 oxygen atoms) / (mass of KClO3)

3. Calculate the percent error in the experiment using the experimental and theoretical values of the mass percent of oxygen. The percent error is defined as:

|(experimental value) - (theoretical value)| / theoretical value * 100%

4. How well does your experimental result match the theoretical value? What sources of error may explain the discrepancy?

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#### Solution Preview

1. Calculate and record the following for the experiment performed with 20g KClO3:

(a) mass of the crucible with manganese(IV) dioxide (in grams): 53.300g

(b) mass of the crucible after potassium chlorate has been added (in grams): 73.300g

(c) mass of the crucible after heating (in grams):

If the mass of potassium chloride is 8.64 g and the mass of crucible is 53.500 g, then, the mass of crucible after heating (that's including potassium chloride) should be 62.14 g (from adding 8.64 g and 53.500 g)

(d) mass of potassium chloride (in grams): 8.64

(e) mass of oxygen ...

#### Solution Summary

This solution deals with calculating results for an experiment that involves 20 grams of KClO3. This solution also answers why discrepancies might exist in the calculations.