Chemistry 30

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There are many quick experiments that can be done to demonstrate the effect of various factors on reaction rate. Any of the four quick experiments in this lab could be replaced with an alternative, which can be found in almost any lab manual that accompanies a student textbook. Alternatively, students could be asked to come up with their own experiments.

The purpose of the lab is for the student to see qualitatively how reaction rates can be altered; no graphing or calculations are involved.

This lab examines the key factors that influence reaction rate:

• Nature of reactants - particle size
• Temperature
• Concentration
• Catalysts

The collision theory should be reviewed before doing the lab.

The lab is divided into four short, simple parts:

 

Part 1. Effect of Particle Size

 The reaction of zinc (powdered vs solid) with hydrochloric acid. Alternative - powdered vs solid calcium carbonate.

Part 2. Effect of Temperature

 The reaction of alka seltzer and water (cold, room temperature, warm).

Part 3. Effect of Concentration

The reaction of zinc with a variety of concentrations of hydrochloric acid.

Part 4. Effect of a Catalyst

Several different solutions are added to a solution of hydrogen peroxide; some of the solutions will catalyze the decomposition reaction and others will have no effect.

Preparation of Solutions & General Comments

3% hydrogen peroxide, H₂O₂ - make sure it is fresh; do not prepare the dilution ahead of time. If no reaction is noted with FeCl₃ try diluting the H₂O₂ less.

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6M HCl - pour 500 mL concentrated HCl slowly into 400 mL distilled water. Dilute to 1 L.

3M HCl - Add 50 mL 6M HCl to 40 mL water and dilute to 100 mL

1M HCl - Add 16.7 mL 6M HCl to 90 mL water and dilute to 100 mL

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0.1 M calcium chloride, CaCl₂ - 1.1 g CaCl₂ per 100 mL water

0.1 M iron(III) nitrate, Fe(NO₃)₃ - 4.0 g Fe(NO₃)₃ ·9H₂O per 100 mL water

0.1 M manganese(II) chloride, MnCl₂  - 1.3 g MnCl₂ per 100 mL water

0.1 M potassium nitrate, KNO₃ - 1.0 g KNO₃ per 100 mL water

0.1 M sodium chloride, NaCl - 0.6 g NaCl per 100 mL water

Expected Results

Part 1. Effect of Particle Size

The powdered forms will react much more rapidly. Caution - be sure to use large test tubes; the powdered reaction may cause excessive foaming.

Part 2. Effect of Temperature

 The reaction will be much faster in the warmer water.

Part 3. Effect of Concentration

Zinc will react much faster with the higher concentrations of acid.

Part 4. Effect of a Catalyst

Catalysts - FeCl₃, Fe(NO₃)₃

Not catalysts - NaCl, CaCl₂, KNO₃

From these results students should realize that the catalyst is the Fe³⁺ ion.