Treyton Steinbeck
12 May 2024
Chemical Kinetics – The Hydrolysis of tert-butyl chloride
Purpose:
In this experiment, we monitor a hydrolysis reaction consisting of tert-butyl chloride
(RCl), sodium hydroxide, and hydrochloric acid. This is done by repeatedly titrating the RCl
with the hydroxide solution to make the solution basic, then waiting for the solution to turn
acidic again. This reaction produces H+ ions until eventually all the added hydroxide becomes
neutralized. We repeat this process 15 times recording volume and the time it takes for the
solution to turn acidic. With this data, we can calculate the number of moles of RCl present
initially and each time we titrated. The objective is to determine the order of the reaction and the
rate constant. We can do this by plotting 3 graphs in excel, one for each order reaction, and
determining which graph is the most linear.
Procedure:
First, we emptied the standardized NaOH in isopropyl alcohol and water solution into a
dry beaker. We prepared a buret for titration by cleaning it thoroughly and filling it with the
NaOH solution. The initial volume of the buret was recorded, and the buret was capped at the top
to prevent evaporation or absorption of CO2. Next, we added the isopropyl alcohol and water
solution into a clean Erlenmeyer flask and added some phenolphthalein as an indicator. NaOH
from the buret was added to the flask until the solution turned pink. Once pink, we added some
tert-butyl chloride to the flask, started the timer, and began gently swirling the flask under the
buret until the solution turned completely colorless. We added more NaOH until pink, then
repeated this process 15 times. Each time the solution turned colorless, the time was recorded
and the volume of NaOH added was recorded. After that, we put the flask on a hotplate to warm
for 30 minutes, keeping the solution at a constant temperature of 50 degrees Celsius. When
ready, we performed one final titration until a light pink color formed. Initial and final volume
were recorded to determine the moles of acid present. Finally, we graphed our data to determine
the reaction order.
Data:
Conclusion:
In the first part, we titrated NaOH and RCl to produce H+ ions to neutralize the NaOH.
From the volume of NaOH added data, we were able to determine the total amount of NaOH
added, which was 30.83 mL. Then, using the molarity of the NaOH we were able to calculate
how many moles of NaOH were used, which was 0.008151 moles. With the time data, we were
able to create a graph of each order process for this experiment using [RCl]t, ln[RCl]t, and
1/[RCl]t. Each graph was very linear, so to determine which order this reaction was, we needed
to compare R2 values. Whichever graph’s R2 value was closest to 1 would determine the order. In
our case, the first-order graph’s value was closest to 1 at 0.9989, so we determined the reaction to
be first-order. With this information, we were able to use the corresponding k value to calculate
the half life of the RCl hydrolysis. After plugging in the k value to the first-order half life
equation, we concluded the half life was 4,131s. Next, we were able to calculate the time
required to hydrolyze, or break down with water, 95% of the RCl if no water had been added or
no heat been applied. We concluded this would take 1.79 * 104s. The main source of error for
this experiment would have to be having some of the NaOH solution leak out of the buret in
between titrations, or during the 30 min heating process. This would cause the moles of NaOH
calculation to be of higher error and would create less accurate graphs.