Name
Lab Day
Preparation and Properties of O2 and H2
Introduction:
In this experiment, oxygen will be prepared by thermal
decomposition of potassium chlorate. The reaction between oxygen and
several elements will be examined. The resulting products will be tested
for acid or base properties.
Hydrogen will then be prepared by the reaction of several metals
with an acid allowing a comparison of relative reactivity of metals.
Finally, the relative reactivity of several acids towards one metal will be
compared.
Experimental:
Preparation of oxygen. Obtain a stopper with glass tubing inserted,
some rubber tubing, 5 glass bottles and glass covers, and a pneumatic
trough. Set-up the apparatus shown below.
KClO3 + MnO2
Bottles filled with water.
To sink.
Bottle filled with water
ready to be placed in the
pneumatic trough.
Weigh out about 6 grams of KClO3. Place this into a 6 or 8 inch
test tube and add a small scoop (about ¼ teaspoon) of MnO2. Thoroughly
mix. It is important that the KClO3/MnO2 mixture be uncontaminated,
since the presence of organic materials could cause an explosion.
Gently heat the KClO3/MnO2 mixture just enough to maintain an
inch of water in the bottles; cover each bottle with a glass square. You
may need to weigh out an additional 6 grams of KClO3 to fill the last 2 or
3 bottles. The equation for the preparation of oxygen is:
2 KClO3
MnO 2
2 KCl + 3 O2
2
Preparation of oxides. Burn the following elements in oxygen gas
using a combustion spoon (below left) or crucible tongs (below center),
keeping the bottles covered with the glass as much as possible. Use the
Fischer burner (below right) for all heating except the Mg & S.
1.
2.
3.
4.
5.
Substance
Magnesium – Ignite a piece of ribbon using the tongs shown
below then thrust into a bottle. Avoid looking at the bright
flame.
Iron – Ignite a ball of steel wool using the tongs below.
Carbon – Use a chunk of charcoal and the tongs below.
Calcium – Grab a small piece using the tongs below and heat
till red hot. Avoid looking at the bright flame.
Sulfur – (In hood only!) Use a small scoop in combustion
spoon.
Observations
Litmus Test*
Magnesium
Iron
Carbon
Calcium
Sulfur
*Test the resulting solutions with 1 drop of Litmus solution. Litmus turns red in acid,
blue in base.
3
Experimental:
Preparation of hydrogen. Place 5 mL of dilute (6 M) hydrochloric
acid into each of 3 test tubes. Add a small piece of Al, Cu, and Pb. Allow
the test tubes to sit for at least 10 minutes. Note any tubes in which a
gas is evolving. Test the gas for hydrogen with a burning splint. Record
your observations below:
Metal
Observations
Hydrogen Test
Aluminum
Copper
Lead
Arrange the metals in order of reactivity towards hydrochloric acid.
Most reactive
,
,
Least Reactive
Relative Reactivity of Acids. Place 5 mL of dilute hydrochloric acid
(HCl), sulfuric acid (H2SO4), nitric acid (HNO3), and acetic acid
(HC2H3O2), into 4 separate test tubes. Into each of the four test tubes,
place a small piece of zinc metal. Compare reactions. Test for the
evolution of hydrogen gas with a burning splint. Record your
observations below:
Acid
HCl
H2SO4
HNO3
HC2H3O2
Hydrogen
Test
Arrange the acids in order of reactivity towards zinc.
Most
reactive
,
,
,
Least
reactive