AP Chemistry Lab

Chemical Analysis of a Mixture



In this experiment a mixture of KCl and KClO3 will be heated until the oxygen containing salt has been converted to KCl:

2 KClO3(s)    2KCl(s)  +  3 O2(g)



Measure a 6 gram sample of the mixture to the nearest 0.001 gram and transfer it to a test tube.  Obtain two gas collection bottles and determine their total volumes using tap water and a graduated cylinder.  Set up a gas collection apparatus as shown below:




When gas evolution slows down decomposition is complete.  When this occurs heat the mixture strongly for one more minute.  Using a glass square over the mouth of the bottle remove the bottle from water and measure the volume of water.  Record the temperature of the water and barometric pressure.





Mass of  KCl/KClO3 mixture:



Volume of collection bottle:



Volume of water:



Volume of gas:



Temperature of water:


Vapor pressure of water: (check out this cool calculator!)  http://s-ohe.com/Water_cal.html)


Pressure of dry O2 gas:


Barometric Pressure:




1.)      Calculate the volume of dry O2 gas at STP.

2.)      Find the moles of O2 gas at STP.

3.)      What mass of KClO3 is found in the sample?




1.)      What is the percentage composition of the mixture? 

2.)      Oxygen gas is slightly soluble in water (this is good news for fish).  How does this slight solubility affect your experimental results?

3.)      What is the density of oxygen gas that was collected at laboratory conditions?

4.)      Calculate the total mass of KCl remaining in your test tube at the end of this experiment.  By what percent should the mass of KCl theoretically increase by?