Factors Affecting Rate of Reaction

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TABLE OF CONTENTS

SECTION 1

Affect of Surface Area on the Rate of Reaction of Alka-Seltzer  

In a successful reaction, reactants have to effectively collide with each other. The chance of a successful collision can be increased or decreased by using many factors. This investigation demonstrates how increased surface area leads to an increased rate of reaction. It is expected that the broken surface area of the Alka-Seltzer tablets has the largest surface area and will have the fastest reaction rate.

MATERIALS/METHODS

  • Materials
  • Safety goggles
  • 2 Film canisters
  • 10-mL graduated cylinder
  • 2 Alka-Seltzer tablets (1.8 g each)
  • Mortar and pestle
  • Balance
  • Stopwatch or timer

  • Procedure
  1. Safety goggles were put on
  2. 10 mL of water was measured in the graduated cylinder and the temperature was recorded
  3. The water was then poured in the film canister
  4. One Alka-Seltzer tablet was crushed using the mortar and pestle
  5.  The mass of the crushed pieces were measured on the balance and poured into the film canister
  6. The lid was then put on firmly on the film canister to close it off to prevent gas from getting in the canister
  7. The stopwatch recorded the time it took for the Alka-Seltzer tablet to react from the time the lead was put on, to when it came off
  8. Appropriate observations were made from the reaction that followed
  9. Repeated steps 1-8, using whole Alka-Seltzer tablets instead of powder
  10. Calculated the data into rates of reaction using the formula g/s

OBSERVATIONS AND CALCULATIONS

Change in the Rate of Reaction: Surface Area

DISCUSSION QUESTIONS

 

This investigation turned out differently than what was hypothesized. The rate of reaction was decreased when the surface area was increased. The rate of reaction of the whole Alka-Seltzer tablet was 0.3 g/s, compared to the 0.0625 g/s, which was the rate calculated using the crushed tablet. When the surface area of the tablet was increased by crushing it into a powder, the rate of reaction decreased 5 times. These results do not make sense since according to the collision model, a solid in a solution can only react when particles  with the surface.
The bigger the area of the solid surface, the more particles can collide with it per second,
and the faster the reaction rate is.

During the experiment, when the crushed tablet was poured in the water, the lid was not put on firmly, leaving a space for air to escape the canister. Decreasing the pressure of a reaction where one of the reactants is a gas (the gas that escaped in this investigation) is similar to decreasing the concentration of a reactant in the solution. As pressure decreases inside the film canister, gas particles will move farther apart and particles will collide less frequently with each other. Therefore, the rate of reaction decreases, similar to what happened in the investigation.

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INCREASING SURFACE AREA:

In this experiment, we chose to change the surface area of the Tums and not the liquid since to increase the surface area of the liquid, we must heat it to evaporate it. By evaporating it, the surface area would increase as the particles moves faster and collide more frequently with each other. However, this reaction rate would then be of raising the temperature, another factor that speeds up reaction rates. Although we have increased the surface area by increasing the space between the molecules, we have also raised the temperature. On the other hand, ...

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