For the following question(s), consider the following reaction mechanism : Step

Question

For the following question(s), consider the following reaction mechanism :

Step 1 2X+Y- W+2Z FAST

Step 2 W+Z- W+U+V SLOW

Step 3 V+Z- 2W+Y FAST

1. THE CATALYST IN THIS REACTION ARE

2. THE RATE LIMITING STEP IN THIS REACTION IS STEP ------------------------, BECAUSE-------------------------------------

a. 1; the first step must occur before any others can occur

b. 3; the last step is always the rate-limiting step

c. 1; it is bimolecular

d. 2; it is the slow step

e. 2; it uses a product of the first step

3. If Pure polonium -210 (k=5.02*10-3day-1) were used in a crime, based on radioactive disintegration alone, how long wwould it take for half the original isotope to disappear?

4. If Polonium-210 emits an alpha particle, the other product will be?

Explanation / Answer

1. The catalyst in this reaction is species Y as it is regenerated at the end of the reaction. Eventhough is it changes it nature during the course of the reaction, since it is reformed during reaction completion in its pristine state without losing the equivalence, it can deduced to play the role of only forcing the reaction to occur in the given mechanism while not being consumed by it, which is the characteristic of every catalyst.

2. OPTION D. Step 2 is considered as the rate-limting step as it takes the maximum time to occur among others. This implies that the formation of products of the 2nd step from those of the 1st step is what consumes the maximum energy as it is either kinetically or thermodynamically least favoured to form. Thus when the reaction overcomes this particular energy hurdle, it achieves completion rapidly. So being the slowest step, the second step serves as the deciding factor for the entire reaction's rate.

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