Lab - Factors Affecting Reaction Rates Name______
Directions: Perform several trials dissolving Alka-Seltzer in water to determine the effect that various properties have on the rate of a reaction.
Part one: Presence of a Catalyst
Obtain two test tubes and fill each one about 1/3 full with 3% hydrogen peroxide solution (H2O2). Both solutions will begin to decompose upon exposure to the air. The decomposition will be evident by the bubbles of oxygen that form. To one of the test tubes, add a single crystal of potassium iodide, which will act as a catalyst.
Analysis:
1. What effect does the catalyst have on the rate of decomposition of hydrogen peroxide?
Part two: Concentration
Fill one test tube about 1/3 full with a 3% hydrogen peroxide solution. Fill a second test tube about 1/3 full with a 30% hydrogen peroxide solution. Add a single crystal of potassium iodide to each test tube.
Analysis:
2. What effect does concentration have on the rate of decomposition of hydrogen peroxide?
Part three: Temperature
Fill two medium sized beakers with 200 mL of tap water. Use the Bunsen burner to heat the water in one of the beakers to at least 50oC. Place an Alka-Seltzer tablet in each beaker and observe which tablet disappears first.
Analysis:
3. What effect does temperature have on the rate of the chemical reaction involving Alka-Seltzer and water?
Part four: Surface area
Fill a medium sized beaker with 200 mL of tap water. Use a mortar and pestle to crush an Alka-Seltzer tablet into a powder. Place the crushed tablet in the beaker and compare the rate at which the tablet dissolves to the cold-water tablet in part three.
Analysis:
4. What effect does surface area have on the rate of the chemical reaction involving Alka-Seltzer and water?
Further analysis:
In order to increase the rate of a reaction, the reactants must collide more frequently. A catalyst is constantly bringing reactants together so they can react. This is why catalysts speed up chemical reactions. Explain why the following also will speed up a reaction.
A) Increasing the concentration of the reactants:
B) Heating up the reactants:
C) Crushing up a solid reactant into a powder:
D) Stirring the reactants:
E) Decreasing the volume for gaseous reactants: