How do you figure out how mch oxygen gas escaped when Potassium Chlorate is decomposed in a reation? Also what mass of Potassium Chlorate was decomposed in the experiment? I conducted the experiement but don't know how to do this.

Here is an example that is worked for you. Just follow the steps.

http://www.jiskha.com/science/chemistry/stoichiometry.html

To determine the amount of oxygen gas that escaped during the decomposition of Potassium Chlorate (KClO3) and the mass of Potassium Chlorate decomposed, you can use the concept of stoichiometry and the ideal gas law. Here's the step-by-step process:

1. Write the balanced chemical equation for the decomposition reaction of Potassium Chlorate:
2 KClO3(s) -> 2 KCl(s) + 3 O2(g)

2. Determine the molar ratio between Potassium Chlorate and oxygen gas:
From the balanced equation, you can see that 2 moles of Potassium Chlorate decompose to produce 3 moles of oxygen gas. Therefore, the molar ratio is: 2 moles KClO3 : 3 moles O2.

3. Measure the volume of the oxygen gas collected:
During the experiment, you need to collect the oxygen gas that is released. Measure the volume of the collected gas using a gas syringe or other suitable apparatus. Make sure to record the temperature and pressure of the gas during the collection.

4. Convert the volume of gas to moles:
Use the ideal gas law, PV = nRT, where P is the pressure, V is the volume, n is the number of moles, R is the ideal gas constant, and T is the temperature in Kelvin. Rearranging the equation, you have n = (PV) / (RT).

5. Calculate the moles of oxygen gas using the ideal gas law:
Using the recorded values for pressure, volume, temperature, and the ideal gas constant (R = 0.0821 L·atm/(mol·K)), calculate the moles of oxygen gas collected.

6. Determine the moles of Potassium Chlorate decomposed:
Since the molar ratio between Potassium Chlorate and oxygen gas is 2:3, multiply the moles of oxygen gas calculated in step 5 by (2/3) to find the moles of Potassium Chlorate decomposed.

7. Convert the moles of Potassium Chlorate to mass:
Using the molar mass of Potassium Chlorate (KClO3), which is 122.55 g/mol, multiply the moles of Potassium Chlorate from step 6 by its molar mass to obtain the mass of Potassium Chlorate decomposed.

By following these steps, you should be able to determine the amount of oxygen gas that escaped during the reaction and the mass of Potassium Chlorate that was decomposed in your experiment.