February 5st 2013
PSU Chemistry 222 – Lab 4
Decomposition of Hydrogen Peroxide
Abstract: This lab was designed to observe the decomposition of hydrogen peroxide into it oxygen and water. The equation for this reaction is H202 H2O + +1/2O2 thus by measuring volume and pressure of O2 generated the amount of O2 generated can be calculated which in turn can be utilized to determine the concentration of water already in the H2O2 solution. The results determined that 3.02% of the solution is composed of H2O2.
This purpose of this experiment was to determine the concentration of liquid water within a given amount of hydrogen peroxide. Because this reaction happens so slowly the addition of the catalyst KI was used. The important things of note within this lab are how the gas was collected, the balanced equation, the partial gas law and the ideal gas law. The gas was collected via a full graduated cylinder inverted within a pool of water. This water was then utilized to displace a volume of oxygen generated by a reaction within a sealed Erlenmeyer flask. The flask emptied into a tube which in turn emptied into the full inverted graduated cylinder. Essentially as gas bubbles form from the reaction they force the water to move aside and the amount of force they generate as well as the volume they displace can then be measured using the cylinders’s calibrated measurements. The Ionic compound Potassium Iodine acts as a catalyst because it disassociated within the solution to K+ and I- ions. The iodine then acts to attract the oxygen molecules away from the hydrogen peroxide transforming it into water. However as more oxygen atoms are freed from water they attract each other strongly creating diatomic oxygen and freeing the Iodine ion to continue catalyzing further reactions. Creating a two step reaction:
H202 (l) + I-(aq) H2O (l) + +OI-(aq)
H202 (l) + OI-(aq) H2O (l) + O2 (g) + I-
Notice that the Iodine is conserved in the...
References: Atkinson (2012) Chemistry 228 Lab Manual. Portland State University.
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