To design an experiment to test the substances [tex]\( X \)[/tex], [tex]\( Y \)[/tex], and [tex]\( Z \)[/tex] to determine which one is a catalyst for the reaction [tex]\( A + B \rightarrow C \)[/tex], follow these steps:
1. Establish a Baseline:
- Perform the reaction without any added substance to establish a baseline reaction time.
- Add 10 mL of [tex]\( A \)[/tex] to 10 mL of [tex]\( B \)[/tex] in a beaker.
- Immediately start a stopwatch when mixing the reactants.
- Observe and record the time taken for the reaction to complete (until bubbles stop forming). Let's denote this time as the "initial reaction time."
Given: Initial reaction time = 20 seconds.
2. Test Substance [tex]\( X \)[/tex]:
- Perform the reaction with substance [tex]\( X \)[/tex].
- Add 10 mL of [tex]\( A \)[/tex] and 10 mL of [tex]\( B \)[/tex] to a beaker.
- Add a small, consistent amount of substance [tex]\( X \)[/tex] to the mixture.
- Start the stopwatch immediately once [tex]\( X \)[/tex] is added to the reactants.
- Observe and record the time taken for the reaction to complete.
Given Result: The reaction with substance [tex]\( X \)[/tex] takes 10 seconds.
3. Test Substance [tex]\( Y \)[/tex]:
- Repeat the process for substance [tex]\( Y \)[/tex]:
- Add 10 mL of [tex]\( A \)[/tex] and 10 mL of [tex]\( B \)[/tex] to a beaker.
- Add the same amount of substance [tex]\( Y \)[/tex].
- Start the stopwatch upon adding [tex]\( Y \)[/tex].
- Observe and record the reaction time.
Given Result: The reaction with substance [tex]\( Y \)[/tex] takes 15 seconds.
4. Test Substance [tex]\( Z \)[/tex]:
- Repeat the process for substance [tex]\( Z \)[/tex]:
- Add 10 mL of [tex]\( A \)[/tex] and 10 mL of [tex]\( B \)[/tex] to a beaker.
- Add the same amount of substance [tex]\( Z \)[/tex].
- Start the stopwatch upon adding [tex]\( Z \)[/tex].
- Observe and record the reaction time.
Given Result: The reaction with substance [tex]\( Z \)[/tex] takes 20 seconds.
5. Analyze Results:
- Compare the reaction times with and without the substances.
- A catalyst is a substance that increases the reaction rate, so it will reduce the reaction time compared to the baseline.
### Conclusion:
Based on the recorded times:
- With substance [tex]\( X \)[/tex], the reaction takes 10 seconds.
- With substance [tex]\( Y \)[/tex], the reaction takes 15 seconds.
- With substance [tex]\( Z \)[/tex], the reaction takes 20 seconds (same as the initial reaction time).
### Determination of Catalyst:
- Substance [tex]\( X \)[/tex] reduces the reaction time from 20 seconds to 10 seconds. Therefore, substance [tex]\( X \)[/tex] is a catalyst.
- Substance [tex]\( Y \)[/tex] reduces the reaction time from 20 seconds to 15 seconds. Therefore, substance [tex]\( Y \)[/tex] is also a catalyst.
- Substance [tex]\( Z \)[/tex] does not change the reaction time, remaining at 20 seconds, so substance [tex]\( Z \)[/tex] is not a catalyst.
Thus, the substances [tex]\( X \)[/tex] and [tex]\( Y \)[/tex] are catalysts for the reaction [tex]\( A + B \rightarrow C \)[/tex], while substance [tex]\( Z \)[/tex] is not a catalyst.
