2. a. What effect was observed on increasing the water from 70 to 80% of the sol

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2. a. What effect was observed on increasing the water from 70 to 80% of the solvent mixture? I need help with all the questions on this page hfee) in t Jtturate à base rate as possible. Record the data in the Table. NOTE: Before beginning each new part of the experiment, the six Erlenmeyer flasks should be rinsed with acetone and drained well. Effects of Temper Prepare two water baths, one warmed carefully on a hot plate to approximately 10° above room temperature, and the second, cooled by the addition of ice, to approximately 10 below room temperature. Repeat the standard technique, but allow the two flasks to equilibrate in the water bath for about five minutes before mixing the solutions. The mixture should also be kept in the bath until the color change has been timed. Maintain- ing constant temperature is critical to the success of this part of the experiment. Repeat each determination three times, and use the average of the three values to determine k at these two additional temperatures. Record the data in your Table. Effect of Solvent The above rate constants are for a solution that is 70% water and 30% acetone. In order to test the effect of solvent polarity, alter the standard procedure as follows: This time, place only 2 mL of the 0.1 Msolution of t-butyl chloride in acetone into Flask 1. Now, place just 0.2 mL of the sodium hydroxide solution, 7.8 mL of water, and the bromophenol blue indicator into Flask 2. Mix as in the standard technique method, and determine the time required for the color change in this 80% water-20% acetone solution. Do three trials as usual, and use the average to determine k. Record all data in your Table. Calculations Compare the average value of k at the three different temperatures. Recall the rule of thumb that by "changing the temperature by ten degrees, the rate is doubled/ halved." Is that what you observed? 1. 70 to 80% of the solvent 2. what effect was observed on increasing the water from a. mixture? b. Does the acetone participate directly in the reaction? What is the function of the acetone? Does the water participate directly in the reaction? what effect would you predict if the solvent were 60% water:40% acetone? c. d. It is not necessary to obtain exactly a 10° change in the temperature, but record the actual temperature used and keep it as constant as possible during the determination. : 94

Explanation / Answer

2. Reaction parameter study

a. When the solvent for the reaction was changed from 70% water to 80% water, the time taken for the color change was shorter. That is the reaction rate was faster. Water being a polar solvent favourd the formation of terty-butyl carbocation intermediate by stabilizing it once formed and facilitate the reaction in the forwards direction.

b. The acetone does not participitate directly in the reaction. The function of acetone is to dissolve the NaX formed after the reaction has taken place.

c. No, the water does not participate directly in the reaction. However it helps in the stabilization of the formed carbocation after the first step of the reaction, thereby enhancing the rate of the forwards reaction.

d. If the solvent was instead 60% acetone and 40% water, the polarity of the solvent has decreased. The rate of reaction would decreases. Such that the color change would occur at a much later time in the reaction.

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