Passage IV

Alcohols are carbon compounds containing a hydroxyl (OH) group. Alkenes are carbon compounds containing at least 1 carbon-carbon double bond (C=C).

Dehydration (removal of H2O) of Alcohol W in the presence of phosphoric acid (H3PO4) produces H2O and a mixture of 4 alkenes (Alkenes 1-4) that each contain only 1 C=C bond:

Dehydration of each of 3 other alcohols (Alcohols X, Y, and Z) produces H2O and 2 or more of Alkenes 1—4. Stu­dents studied the dehydration of each of these 4 alcohols, which are all liquids at 25°C.

Experiment

In each of 4 trials, the students performed Steps 1-5:

1. A 2.30 g sample of Alcohol W, X, Y, or Z was placed in a flask.

2. A 0.5 mL portion of (H3PO4) was added to the flask, and an apparatus for distillation (evaporation of one or more components of a liquid mixture in one vessel and con­densation of the vapors in another vessel) was assem­bled (see Figure 1).

3. The contents of the flask were boiled at 1 atmosphere (atm) of pressure in a heated sand bath. All the compo­nents of the product mixture that distilled before the vapor temperature reached 115 ° C were collected in a test tube that was cooled in ice water.

4. Two mL of saturated salt solution was added to the test tube. The test tube was covered and shaken, and its con­tents were allowed to settle into 2 layers.

5. The percent composition of the top layer (the mixture of alkene products only) was determined (see Table 1).

26. Which of the following statements gives the most likely reason that the test tube was cooled in ice water, as shown in Figure 1? The test tube was most likely cooled in ice water to more readily:

Answer and Explanation

Your Answer is

Correct Answer is G

Explanation

Experimental knowledge questions.

Looking at figure 1, we can see that the connecting conduit on the test tube is the same as the flask, and the gas product after the reaction can enter the test tube through the conduit, and ice water can cool the gas and make the gas cool to a liquid state, so choose G < /p>