Online Chemistry 11 Lab #15

Rates of Reaction

Every group should do section A) and one of either B) or C).  The order you do these in is unimportant, so go where there is space.

A) Copper (II) Sulfate and Iron Reaction

1. Write down a balanced equation for the reaction.
2. Get four test tubes, a test tube stand, samples of iron wire and a stopwatch.
3. Fill three of the test tubes about two thirds full with copper sulfate solution.  Fill the remaining tube (called tube one below!) to about half this amount and add tap water up to the two thirds level.  Place the stand with tubes on a sheet of paper that you can put labels on to keep track of which tube is which.  (The first tube should be the �diluted� one, the second will be �normal�, the third will �double the surface area� one and the fourth will be �heated.�
4. Heat the fourth tube over a bunsen burner until small bubbles begin to form.  DO NOT allow it to boil.
5. Double the long wire over and place it in tube 3.  Place normal wires in each of the other tubes.
6. Note how long it takes (via stopwatch where possible) for the wires to first change to a dark color.
7. Then monitor the solution color and note how long it takes the solution to turn from blue to greenish yellow with the stopwatch.
8. In your analysis you should discuss/explain the observed differences in the rates of reaction in each tube.

B) Decomposition of Hydrogen Peroxide (H₂O₂) using a balloon to measure volume rate of reaction

1. Write down a balanced equation for the reaction.  (I will hopefully do a successful demo to allow you to figure out what one of the products of the decomposition is.)
2. Get a test tube, balloon and a stopwatch.
3. Fill the test tube about 1 cm deep with hydrogen peroxide solution.
4. Look at the solution and note if any bubbles are forming.
5. Add a few grains of manganese (IV) oxide.
6. Redo step 4. 
7. Place the emptied balloon over the open end of the test tube and start the stop watch.
8. Note how long it takes for the balloon to be filled to the point where its skin is becoming tight.
9. Devise a method and carry it out to find the volume of gas that has been produced.  (DO NOT throw out the reactants.  Leave them in the test tube.
10. Now heat up the test tube and contents over a bunsen burner until small bubbles begin to form.  DO NOT allow it to bubble.
11. Repeat steps 7 to 9.
12. Note the grains of manganese oxide.  Do they appear to have been used up in the reaction?
13. Compare the rates of reaction before and after the addition of manganese oxide qualitatively (that is, in words rather than numbers).  What role does the manganese oxide play?
14. Compare the volume reaction rates before and after heating quantitatively (that is, using numbers).  Discuss the results.

C) Decomposition of Hydrogen Peroxide (H₂O₂) using the electronic scale to measure mass rate of reaction

1. Write down a balanced equation for the reaction.  (I will hopefully do a successful demo to allow you to figure out what one of the products of the decomposition is.)
2. Get a 10 mL beaker, stopwatch and go to the electronic scale.
3. Fill the beaker about half way with hydrogen peroxide solution.
4. Look at the solution and note if any bubbles are forming.
5. Place the beaker and solution on the scale and zero the reading by pressing �T.�  (T stands for �tare,� a fancy name for something used as a container.  The idea is to place the empty container on the scale and press this button.  When you add the material to the container then the scale only reads the mass of the added material.  Chemists call the process of subtracting the carrier mass �taring.�)
6. Start the stopwatch and note if the mass has changed at all after about a minute.
7. Add a few grains of manganese (IV) oxide.
8. Redo steps 4 to 6.
9. Carry out a more precise measurement of the mass rate of reaction by rezeroing the scale and timing the mass loss for about 5 minutes.
10. Now heat up the beaker and contents over a bunsen burner until small bubbles begin to form.  DO NOT allow it to bubble.
11. Repeat step 9.
12. Note the grains of manganese oxide.  Do they appear to have been used up in the reaction?
13. Compare the rates of reaction before and after the addition of manganese oxide qualitatively (that is, in words rather than numbers).  What role does the manganese oxide play?
14. Compare the mass reaction rates before and after heating quantitatively (that is, using numbers).  Discuss the results.