The lab report is based on the reactions shown here. In this two-reaction synthe

Question

The lab report is based on the reactions shown here. In this two-reaction synthetic scheme, triphenylmethanol is prepared from bromobenzene, magnesium, ethyl benzoate and diethyl ether. Note that two molecules of “phenylmagnesium bromide” react with one molecule of ethyl benzoate. The molar masses of the reaction participants are: bromobenzene, 157.008 g/mol; magnesium, 24.305 g/mol; ethyl benzoate, 150.17 g/mol; and triphenylmethanol, 260.33 g/mol. Bromobenzene is a liquid. Its density is 1.50 g/mL. Ethyl benzoate is also a liquid. Its density is 1.05 g/mL. Please use the back of this page to show your work. Question 1. If 0.015 moles of ethyl benzoate, 0.0375 moles of bromobenzene, 0.405 moles of magnesium, and unlimited amounts of ether were available in the lab, which of these would be the limiting reagent? Answer: ______________________________________ Question 2. Assume that you used only 0.010 moles of the ethyl benzoate, and that this was the limiting reagent. If you used a 10% excess of bromobenzene in this reaction, how many mL of bromobenzene would you need? Answer: _______________________________________ Question 3. Assume that you used only 0.010 moles of the ethyl benzoate, and that this was the limiting reagent. If you used a 15% excess of magnesium in the reaction, how many grams of magnesium would you need? Answer: _______________________________________ Question 4. What is the theoretical yield of triphenylmethanol (in grams) when 0.010 moles of ethyl benzoate is the limiting reagent? Answer: _______________________________________ Question 5. If you performed the experiment under these conditions and got 2.35 g of triphenylmethanol, what would the percent yield be? Answer: _______________________________________

Explanation / Answer

Question 1: Ethyl benzoate is the limiting reagent.

Given, 1 molecule of ethyl benzoate reacts with 1 molecule of phenylmagnesium bromide to give 1 molecule of triphenylmethanol

Also, given 0.015 mol of ethyl benzoate, 0.0375 mol of bromobenzene and 0.405 magnesium.

Then, 0.0375 mol of  bromobenzene will reacts with 0.405 magnesium to form  0.0375 phenylmagnesium bromide

Finally 0.015 mol of ethyl benzoate should react with reacts with (2 x 0.015 mol = 0.030 mol) of phenylmagnesium bromide to give 0.015 mol of triphenylmethanol

Since, we have phenylmagnesium bromide in excess ethyl benzoate is the limiting reagent.

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