UNDERSTANDING THE ExPERIMENT When the water. solvent and BuCI are mixed, the rea
ID: 530909 • Letter: U
Question
UNDERSTANDING THE ExPERIMENT When the water. solvent and BuCI are mixed, the reaction begins immediately. However, it takes time for all of the solvent to be added. For this reason, the start of the reaction, or zero time, is considered to be half way between the first and final addition of solvent. The IRXl samples cannot be measured directly so we use an indirect method, namely an acid-base titration. This works because, as the overall reaction tells us, every time a molecule of RX reacts, a molecule the Hx, produced: RX HO ROH HX Because of this one-mole-to-one-mole chemical relationship, the following relationships are true: (a) The total amount of H formed at the (time amount of RX which was end of the reaction originally present "zero" time: infinity) is a measure of the This infinity sample, IHxlne is the concentration of HCI after complete, 100% reaction. For the reaction today, the finity sample will sit without for 1 or longer before being titrated. acetone is added to the other timed samples to quench the sample (e stop the reaction) (b) At any intermediate time between "zero" and "infinity", Hx formed is a measure of the amount of Rx that has already unde the amount of rgone reaction, or [HX] mount of RX used up at time "t (original amt of RX) (amt of RX remaining at "t'") Now, although we really want to plot loglRX] against t we can't. However, because of the relationships identified in (a) and (b), we can plot an equivalent log term against log([HX] [HX]) After each titration, you will have the data needed to calculate [Hx, (the concentration of HCI in the sample at time t using the familiar relationship x M, V's x M, where M, [HX] INSTRUCTIONS A. PREPARING FOR THE REACTION. l. Pour about 110-115 mL of the water solvent into an Erlenmeyer flask, cork it and /propanol bring it to the workbenchExplanation / Answer
In the above experiment,
tBuCl is RX
1 mole of RX reacts to form 1 mole of HX
initial [RX]o is concentration at time = 0
at this time concentration [HX]o = 0
after time = t
[RX]t is amount of RX that remained and remaining has reacted to form [HX]t amount
So,
remaining [RX]t = [RX]o - [HX]t
[HX]t = amount of RX that has reacted
So,
[RX]t is the amount of tBCl starting material that remains after some of RX has already reacted to form HX as one of the products.
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