SCH4C                     Lab #4 - Oxides of Metals and Non-Metals
Introduction:   When elements are burned in oxygen, they form compounds called oxides.  In this experiment you will burn several metals and non-metals in oxygen and observe the oxides produced.    The oxides of a number of elements dissolve in water to form acidic or basic solutions.  You can determine if a particular solution is acidic or basic by testing with an acid-base indicator.  Do the oxides of metals behave differently in water than those of non-metals?  In this activity you will be looking for a relationship between the type of element (metal or non-metal) burned and the type of solution (acidic or basic) formed by the oxide.
Problem:  Do solutions of oxides of metals differ from those of the oxides of non-metals?
Apparatus:   crucible tongs, deflagrating spoon, Bunsen burner, hot pad, gas bottles and glass plates
Materials:  litmus paper, or bromothymol blue indicator,  oxygen cylinder, wood charcoal, steel wool, sulphur, magnesium ribbon, sodium metal, distilled water, red phosphorus.
Procedure:
Safety Issues:  Wear safety goggles, Do not look directly at the burning magnesium.  Do not exceed the quantities of elements indicated in the procedure.
1.  Prepare a copy of the data table below to record your observations.
 
Element Burned Metal or Non-Metal Description of oxide Effect of Solution on Litmus or Bromothymol Blue
       
2. Label four gas bottles C, Fe, S and Mg.  Add about 1 cm of distilled water to each bottle.  Fill the bottles with oxygen as instructed by your teacher, and cover each with a glass plate.
3. Heat a piece of charcoal in a deflagrating spoon until the charcoal glows.  Lower the spoon into the bottle labeled C, covering the top of the bottle as much as possible with the glass plate.  See figure above.  When no further reaction occurs, remove the spoon, cover the top of the bottle with the glass plate, and shake the bottle vigorously.
4. Using the crucible tongs, heat a small amount of steel wool until it begins to glow.  Quickly insert the steel wool into the bottle labeled Fe.  When the reaction stops, drop the steel wool into the distilled water, cover the bottle, and shake it vigorously.
5. Heat a very small piece of sulfur in a deflagrating spoon just until the sulfur ignites and then lower the spoon into the bottle labeled S.  When no further reaction occurs, remove the spoon, cover the top of the bottle with the glass plate, and shake the bottle vigorously.
6. Wind a 5 cm length of magnesium ribbon around a pen or pencil to form a tight coil.  Using crucible tongs, ignite the magnesium and quickly lower it into the bottle labeled Mg. DO NOT look directly at the burning magnesium.  Be careful not to let the burning magnesium come in contact with the sides of the glass bottle.  When the reaction stops, drop the steel wool into the distilled water, cover the bottle, and shake it vigorously.
7. Test each of your four solutions with both red and blue litmus paper or bromothymol blue indicator solution and compare the results with a sample of distilled water.
8. Demonstration:   Your teacher will ignite a small piece of sodium in a deflagrating spoon and lower the burning sodium into a gas bottle containing oxygen and 1 cm of distilled water.   When the reaction is finished, your teacher will cover the bottle, shake it, and test the resulting solution with an appropriate indicator.
9. Demonstration:  Your teacher will repeat the above procedure with a small sample of red phosphorus.
Concluding Questions
1. Compare the burning of each element in air and in oxygen.
2. Each of the elements reacted with oxygen to produce an oxide.  Some elements produce two different oxides, depending upon the concentration of oxygen during combustion.  The names of the oxides  formed in this experiment are carbon dioxide, iron(III) oxide, sulphur trioxide and magnesium oxide, sodium oxide and diphosphorus pentoxide.  Write a word equation for the formation of each oxide.
3. Recall that litmus paper turned red in acids and blue in bases.  Bromothymol blue solution turned yellow in acids, blue in bases and is green in neutral solutions.   Which  oxides produced acidic solutions?  Which  oxides produced basic solutions?
4. Does ferric oxide appear to be soluble in water?  Relate this observation with the acid/base test.
5. What type of elements form oxides that produce acidic solutions?  What type of elements form oxides that produce basic properties?
6. Calcium oxide dissolves in water.  Would you expect a solution of calcium oxide to be acidic or basic?
7. Only a small number of meal oxides are soluble in water.  Is it correct to say that metal oxides form basic solutions in water?  Explain.
8.  How does high-sulphur content coal contribute to acid rain?