ACT Science Practice Test 118

Directions: Each passage is followed by several questions. After reading a passage, choose the best answer to each question and fill in the corresponding oval on your answer document. You may refer to the passages as often as necessary.

You are NOT permitted to use a calculator on this test.


PASSAGE V

Students studied the effect of temperature on the conversion rates of two organic acids to their corresponding alcohols. The two organic acids studied were lactic acid (LA) and propionic acid (PA). Each acid was mixed with an Ru/C catalyst (to start the conversion) in an aqueous (water) solution. Lactic acid was found to break down into propylene glycol (PG), water, and various carbon side products. Propionic acid was found to break down into 1-propanol (1-PrOH), water, and various carbon side products. For all experiments, temperature was measured in degrees Kelvin (K).

Experiment 1

Students mixed an LA concentration of 0.5 moles (M) in a 50-milliliter (ml) aqueous solution along with a 5% Ru/C catalyst. The temperature was then varied to study the effect on the rate of conversion from lactic acid to PG. The results are shown in Figure 1.

Figure 1

Experiment 2

Students mixed a PA concentration of 0.5 M in a 50 ml aqueous solution along with a 5% Ru/C catalyst. The temperature was then varied to study the effect on the rate of conversion from propionic acid to 1-PrOH. The results are shown in Figure 2.

Figure 2

1. According to Figure 1, after two hours at 403°K, the percent of LA converted was closest to which of the following?

A. 10%
B. 50%
C. 80%
D. 100%

2. According to Figure 1, at 423°K, the greatest percentage of conversion occurred during which of the following time intervals?

F. 8 to 10 hours.
G. 6 to 8 hours.
H. 2 to 4 hours.
J. 0 to 2 hours.

3. Which of the following was held constant in each of the experiments?

A. The amount of catalyst used.
B. The temperature.
C. The conversion rates.
D. The type of acid used.

4. Based on the data in Tables 1 and 2, which of the following best describes the results of the experiments? As conversion time increased, the percent of acid converted:

F. decreased at some temperatures only until conversion stopped.
G. increased at some temperatures only until conversion stopped.
H. decreased at all temperatures until conversion stopped.
J. increased at all temperatures until conversion stopped.

5. A chemist claimed that the propionic acid conversion rate at 403°K dramatically increases between 8 and 12 hours. Do the results of the experiments support this claim?

A. No; according to Figure 2, conversion stops after 8 hours and does not reach 100%.
B. No; according to Figure 1, nearly 100% of the acid has been converted after 8 hours.
C. Yes; according to Figure 1, there is a significant increase in the conversion rate after 8 hours.
D. Yes; according to Figure 2, less than 50% of the acid has been converted after 8 hours.

6. Based on the results of Experiment 2, assuming that conversion of PA at 423°K continued until it reached 100%, one could predict that 100% of the PA would be converted during which of the following time intervals?

F. < 2 hours.
G. 4 to 6 hours.
H. 12 to 14 hours.
J. < 12 hours.